Believe in geometry, not squaring both sides!

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  • Опубліковано 17 гру 2024

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  • @blackpenredpen
    @blackpenredpen  Рік тому +60

    Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!)

    • @ISoldßinLadensViagraOnEbayఔ
      @ISoldßinLadensViagraOnEbayఔ 11 місяців тому

      I’M JOSEPH STALIN’S MIGHTY FROG

    • @deltalima6703
      @deltalima6703 11 місяців тому +1

      Your "phd friend" video was hilarious, I was laughing about that for hours. The one with the "just identify it" line, the handwaving, and the topology of the circle.
      :D

    • @player3572
      @player3572 11 місяців тому

      Hey bprp! Can you do this math equation? It was in my test.
      sin(cos(tan(x)))=1

    • @leonardobarrera2816
      @leonardobarrera2816 11 місяців тому +1

      But base on the video, you could use the pythagorams inverse formula, also you have on you channel!!!
      It would be more intresting!!

    • @M0n3Y1g
      @M0n3Y1g 11 місяців тому +2

      try explaining this (ANIMATION VS MATH) video explains about mathematics and I still don't understand, can you explain it please?

  • @chaosredefined3834
    @chaosredefined3834 11 місяців тому +542

    I think this is a spot for sybermath's substitution trick.
    Let a = sqrt(16 - x^2). Let b = sqrt(9 - x^2). Then, we are given that a + b = 5. Also, from the definitions of a and b, we have a^2 = 16 - x^2, and b^2 = 9 - x^2. Subtracting those, we get a^2 - b^2 = 7. So, (a + b)(a - b) = 7. But, since a + b = 5, we get 5(a - b) = 7, or a - b = 1.4. Add that to a + b = 5, and we get 2a = 6.4, or a = 3.2. Plugging that back in to a = sqrt(16 - x^2). 3.2 = sqrt(16 - x^2), so 10.24 = 16 - x^2. x^2 = 16 - 10.24 = 5.76 = 2.4^2. So, x = +/- 2.4.
    I will agree, using the "standard" approach of squaring both sides and untangling the mess that that produces is... a giant pain. But, sybermath's substitution trick avoids that nicely.

    • @yoav613
      @yoav613 11 місяців тому +22

      Nice,i like sybermath trick too,but no need for any tricks here.just square sqrt(16-x^2)-5 and -sqrt(9-x^2) and you get after simple algebra x^2=5.76 so x=+-2.4

    • @abdelrahmanayman8415
      @abdelrahmanayman8415 11 місяців тому +10

      I squared both sides (25=16+9-2x^2+2√((9-x^2)(16-x^2))) after that u get x^2=√((16-x^2)(9-x^2))
      Then squaring both sides u will end up 25x^2=16×9
      Solving this simple equation u get postive or negative 12/5

    • @chaosredefined3834
      @chaosredefined3834 10 місяців тому +12

      @@abdelrahmanayman8415 If you are going to square both sides... Subtract one of them first.
      sqrt(16 - x^2) = 5 - sqrt(9 - x^2)
      Then square
      16 - x^2 = 25 - 10 sqrt(9 - x^2) + 9 - x^2
      Rearrange
      10 sqrt(9 - x^2) = 18
      Divide by 10
      sqrt(9 - x^2) = 1.8
      Square
      9 - x^2 = 3.24
      Rearrange
      x^2 = 5.76
      Then solve for x
      x = 2.4 or -2.4
      Notice that you don't have to deal with as big an equation as you did.

    • @samueldeandrade8535
      @samueldeandrade8535 10 місяців тому +5

      sybermath's trick? What makes this trick to be "sybermath's trick"?

    • @Avighna
      @Avighna 10 місяців тому

      That is so fucking cool, thank you so much for sharing this!?!??

  • @BobChess
    @BobChess 8 місяців тому +42

    "Trust in Geometry" people when meet "i"

  • @jarikosonen4079
    @jarikosonen4079 11 місяців тому +191

    Probably a lot of important questions (like up to 3rd deg polynomials) are geometry related.

    • @puleraleaooa8110
      @puleraleaooa8110 11 місяців тому +6

      This is a very interesting question 🙋

    • @d.h.y
      @d.h.y 11 місяців тому

      Euclidean geometry is the future 😆

    • @dominicellis1867
      @dominicellis1867 10 місяців тому +7

      You can always construct a geometric figure that represents an algebraic relationship. That is what makes analysis so beautiful.

    • @dominicellis1867
      @dominicellis1867 10 місяців тому +4

      @@studiouskid1528 if it’s fake, you can just use the half real half fake plane. The noobs call it complex but I’ve always thought it was simple.

    • @dominicellis1867
      @dominicellis1867 10 місяців тому +1

      @@studiouskid1528 2 real axes and one imaginary axis. x->z = a+bi.

  • @basantakumarshaw6440
    @basantakumarshaw6440 11 місяців тому +104

    Now I will use geometry whenever I can to solve funky algebraic equations.

  • @S.sanvi4
    @S.sanvi4 11 місяців тому +983

    That ChatGPT attempt 💀💀

    • @anto8722
      @anto8722 11 місяців тому +187

      “Ai will take over the world!”
      Meanwhile, AIs: “tHrEe pLuS fOuR eQuAlS fIvE”

    • @Macieks300
      @Macieks300 11 місяців тому +27

      It was ChatGPT3.5, not ChatGPT4, so of course it's not going to be good at math.

    • @saj_f0
      @saj_f0 11 місяців тому +82

      @@Macieks300 you say chat GPT 4 is good at math then

    • @Zkflames
      @Zkflames 11 місяців тому +81

      @@Macieks300 gpt 4 is equally garbage at math lmao

    • @Macieks300
      @Macieks300 11 місяців тому +4

      @@saj_f0 Yeah, it's way better at math.

  • @AnthonySouls
    @AnthonySouls 11 місяців тому +20

    I used Google Bard, and this was the best answer I got so far (for anyone interested):
    Prompt: Use geometry and geometric relationships to calculate sqrt(16-x^2)+sqrt(9-x^2)=5
    While the given equation can be solved algebraically, using geometry and geometric relationships adds a visual and intuitive approach. Here's how we can solve it:
    1. Define the geometric elements:
    Imagine a right triangle ABC, where AC = 5 (from the right side of the equation).
    AB and BC are the two roots we need to find, represented by sqrt(16-x^2) and sqrt(9-x^2) respectively.
    Point D lies on AC such that AD = sqrt(16-x^2) and DC = sqrt(9-x^2).
    2. Apply the Pythagorean theorem:
    For both right triangles ABD and BDC, apply the Pythagorean theorem:
    AB^2 = AD^2 + BD^2 = (16-x^2) + BD^2
    BC^2 = BD^2 + DC^2 = BD^2 + (9-x^2)
    3. Combine the equations:
    Add the two equations resulting from the Pythagorean theorem:
    AB^2 + BC^2 = 2BD^2 + 16 - x^2 + 9 - x^2
    Substitute AC^2 for AB^2 + BC^2:
    AC^2 = 2BD^2 + (16 + 9) - 2x^2
    Substitute 5 for AC:
    25 = 2BD^2 + 25 - 2x^2
    4. Solve for BD^2:
    Simplify the equation:
    2BD^2 = 2x^2
    BD^2 = x^2
    5. Relate BD to AB and BC:
    Recall that BD represents the common leg of the two triangles:
    AB = sqrt(BD^2 + AD^2) = sqrt(x^2 + (16-x^2)) = sqrt(16) = 4
    BC = sqrt(BD^2 + DC^2) = sqrt(x^2 + (9-x^2)) = sqrt(9) = 3
    6. Verify the roots:
    Check if the calculated values of AB and BC satisfy the original equation:
    sqrt(16-x^2)+sqrt(9-x^2) = 4 + 3 = 7
    However, since squaring both sides of the original equation introduces extraneous solutions, we need to consider negative values as well.
    7. Negative roots:
    Repeat steps 3 to 6 with negative values for AB and BC:
    -AB = -4, -BC = -3
    sqrt(16-x^2)-sqrt(9-x^2) = -4 - 3 = -7
    This also satisfies the original equation.
    Therefore, the solutions for x are:
    x = ±sqrt(16) = ±4 (positive roots)
    x = ±sqrt(9) = ±3 (negative roots)
    Conclusion:
    Using geometric relationships and the Pythagorean theorem, we found that the equation sqrt(16-x^2)+sqrt(9-x^2)=5 has four solutions: x = ±4 and x = ±3. This approach provides a visual understanding of the problem and the relationship between the squares and square roots involved.

    • @AnthonySouls
      @AnthonySouls 11 місяців тому +4

      Here is the CHATGPT version for the same prompt:
      To solve the equation sqrt(16-x^2) + sqrt(9-x^2) = 5, we can use geometric relationships and algebraic manipulation.
      Let a = sqrt(16 - x^2) and b = sqrt(9 - x^2). The given equation becomes:
      a + b = 5
      Now, let's square both sides of the equation to eliminate the square roots:
      (a + b)^2 = 5^2
      Expand the left side:
      a^2 + 2ab + b^2 = 25
      Replace a and b with their original expressions:
      (sqrt(16 - x^2))^2 + 2sqrt((16 - x^2)(9 - x^2)) + (sqrt(9 - x^2))^2 = 25
      Simplify the expression:
      16 - x^2 + 2sqrt((16 - x^2)(9 - x^2)) + 9 - x^2 = 25
      Combine like terms:
      25 - 2x^2 + 2sqrt((16 - x^2)(9 - x^2)) = 25
      Subtract 25 from both sides:
      2sqrt((16 - x^2)(9 - x^2)) = 0
      Divide both sides by 2:
      sqrt((16 - x^2)(9 - x^2)) = 0
      Now, since the square root of a product is zero only when the product is zero, we can set each factor inside the square root equal to zero:
      16 - x^2 = 0
      Solve for x:
      x^2 = 16
      x = ±4
      and
      9 - x^2 = 0
      x^2 = 9
      x = ±3
      So, the solutions to the equation are x = -4, -3, 3, 4. However, we need to check if these values satisfy the original equation because sometimes extraneous solutions may arise during the manipulation.
      For x = -4:
      sqrt(16 - (-4)^2) + sqrt(9 - (-4)^2) = sqrt(0) + sqrt(7) = 0 + sqrt(7) ≠ 5
      For x = -3:
      sqrt(16 - (-3)^2) + sqrt(9 - (-3)^2) = sqrt(7) + sqrt(0) = sqrt(7) ≠ 5
      For x = 3:
      sqrt(16 - 3^2) + sqrt(9 - 3^2) = sqrt(7) + sqrt(0) = sqrt(7) ≠ 5
      For x = 4:
      sqrt(16 - 4^2) + sqrt(9 - 4^2) = sqrt(0) + sqrt(7) = 0 + sqrt(7) ≠ 5
      None of the solutions satisfy the original equation. Therefore, there are no real solutions to the given equation.

    • @bmn6292
      @bmn6292 10 місяців тому

      @@AnthonySouls The error in this calculation is that when you removed 25 from both sides, you also removed -2x^2 from the left side without adding 2x^2 to the right side.

  • @rekikhayder
    @rekikhayder 11 місяців тому +36

    Great simple geometric solution 😊

  • @gusmichel7035
    @gusmichel7035 2 місяці тому +1

    At 3:30, getting x is easier by similar triangles. Each small triangle is similar to the large one by AA theorem, as they share an angle and also have a right angle. Using the left triangle, you get x/4=3/5, and on the right you get x/3=4/5. In either case, multiply by the denominator on the left to get x=12/5.

  • @sifilo
    @sifilo 11 місяців тому +17

    I'm loving this series of yours, the "Believe in __ not ____". Could we get a trigonometry edition?

    • @blackpenredpen
      @blackpenredpen  11 місяців тому +10

      Great idea! I will have to think about it.

  • @patum3588
    @patum3588 11 місяців тому +43

    Also there exist inverse pythagoran where 1/a^2 + 1/b^2 = 1/d^2 so in our case it would be : 1/4^2 + 1/3^2 = 1/x^2 and it would be equal to this anwswer

    • @ЕгорМедведев-ч3ш
      @ЕгорМедведев-ч3ш 5 місяців тому

      1. Firstly, we should determinate a solution space, if we working with real numbers:
      (16 - x² ≥ 0) & (9 - x² ≥ 0);
      ((4 - x) × (4 + x) ≥ 0) & ((3 - x) × (3 + x) ≥ 0);
      (- 4 ≤ x ≤ 4) & (- 3 ≤ x ≤ 3);
      - 3 ≤ x ≤ 3.
      Last string is the solution space of our equation in real numbers.
      2. Also we can use geometric mean formula, because we have an altitude from right angle in rectangular triangle ("x" is the length of it):
      x = sqrt (sqrt (16 - x²) × sqrt (9 - x²));
      x = sqrt (sqrt ((16 - x²) × (9 - x²));
      x⁴ = (16 - x²) × (9 - x²);
      x⁴ = 16 × 9 - 16 x² - 9 x² + x⁴;
      x⁴ = 16 × 9 - 25 x² + x⁴;
      0 = 16 × 9 - 25 x²;
      25 x² = 16 × 9;
      25 x² - 16 × 9 = 0;
      (5 x)² - (4 × 3)² = 0;
      (5 x - 4 × 3) • (5 x + 4 × 3) = 0;
      1) 5 x - 4 × 3 = 0;
      5 x = 4 × 3;
      x = 4 × 3 / 5;
      x = 12 / 5;
      x = 2,4.
      2) 5 x + 4 × 3 = 0;
      5 x = (- 4) × 3;
      x = (- 4) × 3 / 5;
      x = - 12 / 5;
      x = - 2,4.
      3. Both of values of "x" entered in our solution space, because - 3 ≤ - 2,4 ≤ 2,4 ≤ 3 - is right inequality, that is why answer is: x = ± 2,4 (in real numbers).

  • @sergeygaevoy6422
    @sergeygaevoy6422 11 місяців тому +67

    It is sort of isomorphic transform I think. Like Laplace or Fourier transfom. Many things are isomorphic even when they are very different.

    • @table5584
      @table5584 11 місяців тому

      Isomorphisms!

    • @pauselab5569
      @pauselab5569 11 місяців тому

      don't think that it is an isomorphism at least not in the usual sense.

    • @sergeygaevoy6422
      @sergeygaevoy6422 11 місяців тому

      @@pauselab5569 You can map some structure to another structure (sqrt() to a triangle). Map some operation to another operation (addition to position in space). Then you should unmap the result.
      The only problem here that we cannot get the negative result in geometry. We cannot be sure there no other colutions using this mapping. That is true.
      But we do have ideal mappings: quaternions ~ 2x2 matrices,
      all quaternion with the same vector direction ~ complex numbers (a plane in 4D)
      multiplication of complex numbers & quaternions ~ rotations (quaternions have parallel and orthogonal parts rotate differently)
      The more interesting question lies in Physics: DO gravity and electromagnetism share the same nature OR are they only isomorphic!? If two thing follow the same axioms they will follow the same theorems.

    • @samueldeandrade8535
      @samueldeandrade8535 10 місяців тому

      What ... are you talking about?

    • @alextaunton3099
      @alextaunton3099 10 місяців тому

      ​@@samueldeandrade8535isomorphisms. Get with the program

  • @ricardoguzman5014
    @ricardoguzman5014 11 місяців тому +2

    Nice way to solve. I solved a variation of this problem earlier this year based on a video posted by Peyam. There's an amazing detail contained in the problem. x² = 4² - [√(16-x²)]². x² = 3² - [√(9-x²)]². So 4² - [√(16-x²)]² =3² - [√(9-x²)]². Add [√(16-x²)]² and [√(9-x²)]² to both sides of the equation and you get 4² + [√(9-x²)]² = 3² + [√(16-x²)]². And so you obtain a variation of a pythagorean quadruple, a² + b² = c² + d². By using different values for the side lengths and perpendicular of the triangle, you can generate an infinite number of rational or whole number solutions to the problem of finding a² + b² = c² + d².

  • @DeclanPeterson-s8n
    @DeclanPeterson-s8n 11 місяців тому +4

    This is not for to the video, but just for those who see this including blackpenredpen. I found a potential formula for the summation of 1/x^n where n is greater than or equal to 1. d^n / d r^n { ln[ (x+r-1)! / (r-1)! ] }/n! with r being a constant equaling 1. ( Note I used d for the partial derivative of r).

    • @DeclanPeterson-s8n
      @DeclanPeterson-s8n 11 місяців тому +1

      It is actually d/dr {ln[ d^(n-1) / dr^(n-1) (x+r-1)!/(r-1)!]} and the bounds of summation are 1 and infinity.

  • @3rpi3r44
    @3rpi3r44 11 місяців тому +2

    Really cool problem! Thank you as always

  • @dankestlynx7587
    @dankestlynx7587 8 місяців тому +1

    i used angles to find the value of x in the end , assume one angle tetha rest are either 90-tetha or tetha which makes it much easier

  • @SteveMathematician-th3co
    @SteveMathematician-th3co 11 місяців тому +11

    This is gold! Thank you for such a useful video!

  • @TheQuadraticFormula319
    @TheQuadraticFormula319 11 місяців тому +15

    I have always loved the geometrical representation of equations (mostly from 3blue 1brown) but this method is just ♥

    • @2001herne
      @2001herne 10 місяців тому +1

      You learn to love geometric representations in engineering - on the engineering HSC (Australia(NSW) Higher School Certificate) exam it's valid to solve force diagram problems either analytically, or by drawing the diagram to scale and measuring. If you're neat enough, it's a lot quicker, and about as accurate.

  • @travisretriever7473
    @travisretriever7473 10 місяців тому +1

    *Standing Ovation!*
    Always lovely to see elegance in math problems like this. :)

  • @shivannda
    @shivannda 15 днів тому

    This is great. The numbers work very well. Thank you for that.

  • @ДмитроМиколайович-ь7п
    @ДмитроМиколайович-ь7п 11 місяців тому +2

    Glad to see you again!
    Nice solution!

  • @meshiraj
    @meshiraj 11 місяців тому +11

    The Solution was pretty impressive . When I glanced at the video's thumbnail, my instinct told me the answer might be something like the square root of 5, and it turned out to be true since the square root of 5 is roughly 2.4.
    Here's how I approached it:
    I focused on the second part of the equation, Sqrt(9-x^2), and thought that for any x to make the equation true, this part must be a perfect square. Since it's 9 minus something, and the nearest square (less than 9) is 4, I realized that the subtracted value of x must be 5 to make it work. Voila! When I cross-checked this value with the first part, Sqrt(16-x^2), and calculated with calculator it fits to say that LHS = RHS! :)

  • @sowhanQ
    @sowhanQ 8 місяців тому +7

    What about them complex roots

    • @TazwaarAhmed09
      @TazwaarAhmed09 28 днів тому +1

      for quadratic (max value of exponent is 2) equations as we can see here, theres a maximum of 2 solutions, including complex and real solutions
      here, theres 2 solutions an both are real, therefore there are no imaginary/complex solutions
      generally, a polynomial equation with a maximum exponent/power of "n", has upto "n" solutions, including both real and complex solutions.. so here theres no complex roots

    • @stranger0152
      @stranger0152 19 днів тому +1

      @@TazwaarAhmed09 Just because it has x^2 max term doesn't mean an equation like that is quadratic. Equation in the video is not quadratic. Also not polynomial.

  • @FreakBoyFarty
    @FreakBoyFarty 8 місяців тому +73

    He used a blue pen

  • @Perfectionist-i6z
    @Perfectionist-i6z 11 місяців тому +2

    Question) If Y={x such that x is a positive factor of the number [(2^p-1)(2^p - 1)] , where (2^p - 1) is a prime number}. Write Y in the rooster form

  • @Tamir_Karniely
    @Tamir_Karniely 11 місяців тому

    I thought about an interesting question and I couldn't solve it. I suggest it as a video idea:
    Consider the function
    f(x) = Sigma from n=1 to x of (1/n)
    Where x is a Natural number.
    Now plot points on a regular x-y plain, where the x-values are the x value of f(x), and y-values are the Smallest Common Denominator of all fractions created by f(x) at that x. In short, a coordinate is: (x, SCD).
    For clarrification, the first few points are: (1,1), (2,2), (3,6), (4,12), (5,60), (6,60), (7,420), (8,420), (9,3690), (10,3690)...
    The goal is to find the function g(x) that outputs the SCD according to f(x) for every input x, where x is Natural.
    Bonus: if possible, expand the definition of g(x) so that the input is in the Real domain.

  • @phat_khiep
    @phat_khiep 11 місяців тому

    There are n multiple choice questions, each question has i options to choose from.
    Step 1: Randomly choose the mth option (with m less than or equal to i and m greater than or equal to 1) in the first multiple choice question
    Step 2: Repeat the option in the 1st multiple-choice question in the next (k-1) multiple-choice questions.
    Step 3: To choose the option in the (k+1) multiple choice question, we will choose in the following way for each case:
    Case 1: If the option chosen in the kth multiple choice question is the mth option (with m smaller than i), then choose the (m+1)th option.
    Case 2: If the option chosen in the kth multiple choice question is the ith option, then choose the 1st option.
    Step 4: Repeat Step 2 and Step 3 for multiple-choice questions from the (k+2)th multiple-choice question to the nth multiple-choice question.
    Each multiple choice question has only 1 correct answer. Let t be the number of multiple-choice questions answered correctly in n multiple-choice questions, t follows the Bernouli distribution. Find k to t max.

  • @mike1024.
    @mike1024. 9 місяців тому

    That was a neat approach to this problem! When I read the title, I thought more about circles than right triangles.

  • @StereoSpace
    @StereoSpace 9 місяців тому

    I would never have thought of approaching the problem that way. Very interesting!

  • @Aaron-q9p4h
    @Aaron-q9p4h 4 місяці тому +1

    Thank you, so much 😊

  • @Sirius37641
    @Sirius37641 10 місяців тому +1

    Q: can you solve x^4+x^2+1=0 by using the quadratic formula?
    .
    .
    .
    Ans: yes
    (x^2)^2+x^2+1=0, and now we have a quadratic equation in terms of x^2
    x^2=-1+-sqrt of 1^2-4(1)(1)/2(1)
    x^2=-1+-isqrt of 3/2, and now take the square root of both sides, we get:
    x=+-sqrt of( -1+-isqrt of 3/2), and now we can square both the numenator and the denominator, we get:
    x=+-i+-isqrt of 3/2
    (x is equal to plus or minus i plus or minus the square root of 3 all over 2)

  • @glogenuniversal6047
    @glogenuniversal6047 10 місяців тому +1

    This was fun! thank you for your videos

  • @navyntune8158
    @navyntune8158 10 місяців тому +1

    √(16-x²) + √(9-x²) = 5
    √(4²-x²) + √(3²-x²) = 5
    Notice that there's a Pythagorean Theorem thing going on
    Draw one right triangle with one side being x long, and the hypotenuse 4 long. The bottom side is unknown.
    Draw another right triangle, with the hypotenuse being 3 long this time. The bottom side is, again, unknown.
    Connect the triangles at the x long side. The bottom sides should add up to 5
    Now we have a large triangle with a 3:4:5 side ratio, the iconic Pythagorean ratio. The 3 long and 4 long sides are perpendicular.
    Use the big triangle's area to calculate x. Notice that it is x tall.
    3 • 4 / 2 = 5x / 2
    x = 12 / 5
    x = 2.4

  • @1tubax
    @1tubax 11 місяців тому +4

    Im gonna use this question to show my friends that geometry is beautiful and not just shapes

  • @zhelyo_physics
    @zhelyo_physics 11 місяців тому +2

    Super interesting video!

  • @panyachunnanonda6274
    @panyachunnanonda6274 9 місяців тому +1

    Wow, Thank you, so amazing, I love this technique.

  • @devtated8213
    @devtated8213 9 місяців тому +1

    Just noticed that even x = 0 as well as x= +- 12/5
    Since, we are using the 3-4-5 triplet to find the results
    The one of the trivial solutions to the problem!!
    Awesome explanation!!!!
    Looking forward to more such videos

    • @GrimAxel
      @GrimAxel 9 місяців тому

      Except x=0 doesn't work. When x=0, sqrt(16-x^2)=4 and sqrt(9-x^2)=3. But 4+3=7, and 7≠5.

  • @yourgarage4175
    @yourgarage4175 8 місяців тому +1

    we can also able to do this in another way:
    ✓16-x²=(5-✓9-x²)
    then we can square both sides
    it will be very easy

  • @jadewolf3416
    @jadewolf3416 11 місяців тому +2

    This will be a very good watch!

  • @mokouf3
    @mokouf3 11 місяців тому +3

    1: If the resulting triangle isn't a right triangle, we can use Heron's formula.
    2: Haha, ChatGPT did it wrong again! ChatGPT is not good at math, but quite good at programming!

  • @EmpyreanLightASMR
    @EmpyreanLightASMR 11 місяців тому +7

    On a recent StarTalk podcast episode, Prof. Charles Liu said on his (presumably at-home) exams, he asks his students to use chaptgpt to solve a problem, and then to explain why it's wrong 😂

  • @nathanjiang100
    @nathanjiang100 11 місяців тому +10

    I was hoping you’d use the inverse pythagorean theorem 1/a^2 + 1/b^2 = 1/h^2 then you get 1/x^2 = 25/144 so x = +/- 12/5

  • @agnichatian
    @agnichatian 10 місяців тому +2

    Even without the perfect numbers leading to the second right triangle, Heron's formula can be used to get the second relation for the area: let semiperimeter s = (a+b+c)/2 then area A = sqrt[ s(s-a)(s-b)(s-c) ]. In this problem s is 6 and A is also 6.

  • @thatapollo7773
    @thatapollo7773 11 місяців тому +1

    After making the triangle, instead of equations areas you can use the "inverse" Pythagoras theorem ie 1/x^2 = 1/3^2+1/4^2

  • @hdsjshheishhs1907
    @hdsjshheishhs1907 11 місяців тому +2

    Try this:
    1+power(2+power(3+…+power(n+…,1/n),1/3),1/2)=?where n is natural and goes to infinity.

  • @kingbeauregard
    @kingbeauregard 9 місяців тому +1

    I did this one the brute force way, and it was surprisingly not too bad. It was a miracle of canceling terms so that it solved pretty neatly.

    • @eBusinessjma
      @eBusinessjma 6 місяців тому +1

      Yeah, square, cancel terms, square, and you are done. If the numbers were different and stuff didn't cancel nicely we'd have had to solve a quadratic equation along the way (scary!), but we'd still get a solution. I can't help but feel like there is a very wrong lesson in this, you can't count on always getting nice equations in the wild, looking for an elegant way, rather than just a way, to solve something is most often a waste of time.

    • @kingbeauregard
      @kingbeauregard 6 місяців тому

      @@eBusinessjma Sure; by all means take a minute to look for an inspired way to approach a problem, but don't expect there will be one.

  • @Aaron-q9p4h
    @Aaron-q9p4h 4 місяці тому +1

    Thank you, so much

  • @ahandas3299
    @ahandas3299 Місяць тому

    As soon as I saw the problem ,I knew what you were going to do

  • @Sriansu-to4ds
    @Sriansu-to4ds 10 місяців тому

    I used rationalisation and it also works here. On rationalising (16-x²)½+(9-x²)½=5,
    We get (16-x²)½-(9-x²)½=7/5.
    Adding both equations we can eliminate one term and square the resulting equation to get x.

  • @spacetimeslasher
    @spacetimeslasher 11 місяців тому +2

    Imperial!
    As an math aspirant i will use it

  • @ppmax9392
    @ppmax9392 11 місяців тому +1

    May i ask since n[sin(180degree/n)] helps u calculate pi. If lim n--> infinity, is n(sin(180degree/n)) = pi?

    • @ppmax9392
      @ppmax9392 11 місяців тому

      anyone answer me pls ty

  • @AyberkDurgut
    @AyberkDurgut 11 місяців тому +1

    Great solution!

  • @manyifung5411
    @manyifung5411 11 місяців тому +1

    If it is not right angled triangle we can use 1/2 ab sin(x) to find the area

  • @hanswust6972
    @hanswust6972 18 днів тому

    Wonderful solution!

  • @Kambyday
    @Kambyday 2 місяці тому

    Trust in algebra too
    Let 9-x² = y²
    => x² = 9-y²
    Plugging it in our equation, we get
    √(7+y²) + y = 5
    7 + y² = (5 - y)²
    7 + y² = y² - 10y + 25
    10y = 18
    y = 9/5
    Now,
    x²=9-y²
    =9-(9/5)²
    =144/25
    x=±12/5

  • @giovannicorno1247
    @giovannicorno1247 8 місяців тому

    Brilliant, I did not think to use build the second triangle in that way. I made a mental calculation and found sqr 7 is a good solution😊.

  • @General12th
    @General12th 11 місяців тому

    I always love having a look inside!

  • @juliomora9151
    @juliomora9151 9 місяців тому

    La longitud de la altura referida a la hipotenusa en un triángulo rectángulo es igual al producto de los catetos dividido por la hipotenusa, x=(3*4)/5

  • @samarjitdasIISERkol
    @samarjitdasIISERkol 9 місяців тому

    4:24 I would have used Heron's formula for the area of the triangle here and equate it with (5×)/2 😂😂

  • @mahdikissoum2913
    @mahdikissoum2913 11 місяців тому +3

    Hi Blackpenredpen, I have two things to tell you! First of all, could you make the 100 integrals file (the first video) freely available? Secondly, I offer you a huge integral! The integral of 1/(1+x^5). Otherwise good luck! Bye !

  • @gopalsamykannan2964
    @gopalsamykannan2964 11 місяців тому

    Very good teaching. Thank you !

  • @rambutan_lychee9255
    @rambutan_lychee9255 11 місяців тому +1

    I never even thought about it before, yet it just seem intuitive enough to work soo well. Thank you for the educational video.

  • @k.turtle6145
    @k.turtle6145 9 місяців тому

    You can also say the triangles are similar and create a ratio of the side lengths to the hypotenuse. 4/5 = x/3

  • @Vanessa.W
    @Vanessa.W 10 місяців тому +1

    Can you try the integral of x/sinh(x) from -∞ to ∞? It comes out to a really nice answer, but I have no idea how you’d actually solve it…

  • @6JEMS
    @6JEMS 11 місяців тому +1

    老师可以讲一下怎么积分Tan(cos(x)) 从0 到2pie吗

  • @EyeSooGuy
    @EyeSooGuy 10 місяців тому

    Hey there, Steve. Since I’m in Info Tech, I also had to learn CS (computer science). The whole new other “dimensions” of math like binary (0 and 1), octal (0 to 7) … I’m skipping the decimal part bc that’s the math we’re at right now …. Hexadecimal (base-16 that’s 0 to 9 and A to F representing 10 to 15. Like 1F for example …. That’s 31 in decimal and so forth. You get the gist), base-32, base-64 and finally, base-85.
    I learned there’s a multiplication table of hexadecimals. Google it up all you want.
    Now! I’m curious. Can you do algebra, trig, geometry and/or even calculus WITH only hexadecimals?
    I’d LOVE to see a vid of you attempting on applying the Euler and the pi to hex format. Hehe. Pretty please?! Can you do that?! You can even consult with a comp sci expert on this, if CS is not your expertise. Wink.

  • @DAOHAPUR
    @DAOHAPUR 9 місяців тому

    Damn...I was always an algebra guy but now I think geometry also kicks. Thanks sir.

  • @mausmalone
    @mausmalone 9 місяців тому

    I got the answer but instead of using the area of the triangle I used simple ratios. Because I know two angles of the right side triangle, I know that it ALSO is a 3-4-5 triangle, so its sides would have the same ratios as any other 3-4-5 triangle. That gave 3/x=4/5. Very very easy to calculate.

  • @martys9972
    @martys9972 10 місяців тому

    Very nice solution! While it is true that the solution would not be as nice if the RHS were not equal to 5, the geometrical method works for those cases as well, since the area of the triangle can be obtained by Heron's formula. For RHS = 6, the answer is +/-sqr(455)/12.

  • @ludmilaivanova1603
    @ludmilaivanova1603 10 місяців тому

    very interesting approach!

  • @zeroplays9915
    @zeroplays9915 11 місяців тому

    Can you make a video about this interesting problem--> If z = x + iy is a complex number where x and y are integers. Then, the area of the rectangle whose vertices are the roots of the equation----> w z^3 + z w^3 = 350, where w=conjugate of z

  • @AvindՏhrma
    @AvindՏhrma 8 місяців тому +1

    0:53.............................ya don't believe in squaring both the sides but believe in taking square root on both sides.... 😌

  • @Nikioko
    @Nikioko 10 місяців тому

    Euclid's Height Theorem: h² = pq
    Euclid's Leg Theorem: a² = cp, b² = cq

  • @Punchbadguy
    @Punchbadguy 8 місяців тому +1

    Wouldnt the negative still be extraneous since it's asking for a measurement? Yes negative measurements can exist but it doesn't really make sense in this case

    • @iamthesaltonyourwounds2313
      @iamthesaltonyourwounds2313 8 місяців тому

      Well the original question doesn't ask for a measurement it just asks for the value of x, he just used geometrical terms to solve this equation in another manner, obviously if you use geometry you will only deal with positive values, but since the original question is algebraic we can also have negative values for x

  • @ronaldokado834
    @ronaldokado834 8 місяців тому

    Congratulation! It is fantastic!!!

  • @someonespadre
    @someonespadre 8 місяців тому

    For this to work the larger triangle has to be a right triangle.
    No, I was wrong here. Consider a 13-14-15 triangle. Used Heron’s formula to get area=84 and height above 15 side is 11.2.
    Sqrt(169-x^2)+sqrt(196-x^2)=15, x=+/-11.2. This is great.

  • @Flukeworm
    @Flukeworm 10 місяців тому

    Respected sir,
    Find the value of the following questions geometrically in the principle value range:
    (a) arcsin(sin 23)
    (b) arcsin(sin24)
    Where both 23 and 24 are in radian.

  • @BrianDuVeznan
    @BrianDuVeznan Місяць тому

    Even though substituting 9 - x^2 as M might be a better method, this is a very interesting!!

  • @stanislavbutsky8432
    @stanislavbutsky8432 10 місяців тому

    I just multiplied both sides to a conjugate sqrt(16-x^2)-sqrt(9-x^2) that resulted in sqrt(16-x^2)-sqrt(9-x^2)=1.4 then I simply used the Gauss method and summarized this equation with the source one so 2sqrt(16-x^2)=6.4 => sqrt(16-x^2)=3.2 => 16-x^2=10.24 => x^2=5.76 => x=+-2.4

  • @anthonyr.748
    @anthonyr.748 11 місяців тому

    with similar triangles you can see the answers with ratios (either sub triangle works), 5 : 3 as 4 : x implies x=12/5

  • @IRanOutOfPhrases
    @IRanOutOfPhrases 11 місяців тому +1

    Lol.... ChatGPT really bombed that question.

  • @harrymatabal8448
    @harrymatabal8448 10 місяців тому

    I know it has to do with theorem of Pythagoras. But I am still thinking. Excellent question.

  • @GamingYT-yd1hd
    @GamingYT-yd1hd 8 місяців тому

    There's also a nice algebraic solution:
    Multiply by the conjugate nd we get 7/5=√(16-x²) -√(9-x²)
    Then we add the first eq nd divide by 2 we get √(16-x²)=16/5 nd then we end up gettin the same result 👩🏻‍🎤

  • @shameem-gy1pm
    @shameem-gy1pm 11 місяців тому +1

    Can we integrate cosx*e^(-cosx)
    Pls reply

  • @thefreeze6023
    @thefreeze6023 11 місяців тому +1

    Hi BlackPenRedPen! Could you please make a video about solving: i ^ x = x ? I have tried it, but I keep arriving at the wrong solution, and I cannot find explanations online. I tried to get the maximum amount of complex solutions by using all branches of Lambert W Function and using all possible theta values to represent i as e^(i*theta). But it is wrong on WolframAlpha. Can you please help?

    • @ttmfndng201
      @ttmfndng201 10 місяців тому

      I got this:
      i^x=x,
      x=e^i(pi/2+2piN)x, (where N is an integer)
      x=cos((pi/2+2piN)x)+isin((pi/2+2piN)x).
      if x=a+bi:
      a+bi = cos((pi/2+2piN)a+(pi/2+2piN)bi)+isin((pi/2+2piN)a+(pi/2+2piN)bi)
      I'll say M=pi/2+2piM to make things shorter, so
      a+bi=cos(Ma+Mbi)+isin(Ma+Mbi)
      a+bi=cos(Ma)cos(Mbi)-sin(Ma)sin(Mbi)+isin(Ma)cos(Mbi)+icos(Ma)sin(Mbi)
      a+bi=cos(Ma)cosh(Mb)-isin(Ma)sinh(Mb)+isin(Ma)cosh(Mb)-cos(Ma)sinh(Mb)
      now you can make a system with the real and imaginary parts:
      a=cos(Ma)cosh(Mb)-cos(Ma)sinh(Mb)
      b=sin(Ma)cosh(Mb)-sin(Ma)sinh(Mb)
      a=cos(Ma)(cosh(Mb)-sinh(Mb))
      b=sin(Ma)(cosh(Mb)-sinh(Mb))
      a=cos(Ma)*e^-(Mb)
      b=sin(Ma)*e^-(Mb)
      a*e^(Mb)=cos(Ma)
      b*e^(Mb)=sin(Ma)
      from the first equation, b=ln(cos(Ma)/a)/M
      dividing the second equation by the first, b=a*tan(Ma)
      putting them together, Ma*tan(Ma)=ln(cos(Ma)/a) and once you have a solution for a, to find b you just use b=a*tan(Ma)
      plotting with desmos and looking for approximations gave me approximate answers that work but I don't know how to get exact answers.
      Wolframalpha's answer seems a bit suspicious to me since it fails to give even an approximate answer, and is unable to calculate W(-i*pi/2), which it says is part of the answer, but I don't know enough to know whether what wolfram is saying is right.

  • @ttmfndng201
    @ttmfndng201 10 місяців тому

    before watching the video: this can be rewritten as sqrt(16-x^2)=5-sqrt(9-x^2) These are the equations of semicircles, so basically the intersections between a circle of radius 4 with center in (0,0) and a circle of radius 3 with center in (5,0). These form 3-4-5 right triangles, so the distance of the intersection from the hypotenuse is 3*4/5=12/5. The solutions are x=12/5 and x=-12/5

  • @menaa5978
    @menaa5978 11 місяців тому

    You can use this method:
    Suppose we have a right triangle where AB^2 + AC^2 = BC^2 and BC = BD + DC
    So the height AD which is x in this video's case will be AD ^ 2 = BD * DC
    And then you can solve the problem.
    Right, isn't it?

  • @Ty2005nm
    @Ty2005nm 11 місяців тому +1

    Please, I want you to create a formula to solve the equation
    ax^3+bx^2+cx+b
    And this one too
    ax^3+bx=n

  • @eknathraykar3572
    @eknathraykar3572 10 місяців тому

    Nice approach.

  • @christianchan1144
    @christianchan1144 11 місяців тому

    can this be generalized for solutions of the form: sqrt(a^2 - x^2) + sqrt(b^2 - x^2) = c where a,b,c are a recognized pyth. triple?

  • @deepeshsinghthakur6427
    @deepeshsinghthakur6427 21 день тому +1

    I don't know why this is made so complicated
    It is clearly x=0

  • @xicad1533
    @xicad1533 10 місяців тому

    How do we do a multivariable limit using epsilon-delta method?

  • @fletch7311
    @fletch7311 11 місяців тому

    would you be able to do a video explaining how to solve equations such as 2^x + 3^x = 2 or 2^x + 5^x = 1 and other similar cases?

  • @alexandermorozov2248
    @alexandermorozov2248 8 місяців тому

    Любопытно! Хорошо бы ещё провести проверку 😘

  • @kylebeschler03
    @kylebeschler03 11 місяців тому

    what was up with holding that red white and black stuffed looking thing in the past? I was curious when i saw your past vids. Interesting content btw! Very creative, different, and analytical.

  • @BasedMathLover
    @BasedMathLover 11 місяців тому

    That was a cool problem Thank you 😊

  • @IdiotThings-f5c
    @IdiotThings-f5c 11 місяців тому

    I'm your silent fan, I really love the way you help us in math, especially me but, I am curious. How did you become master at math? how much time do you solve math before? can you make a video for it?

  • @mikezilberbrand1663
    @mikezilberbrand1663 9 місяців тому

    Well done, Alan!

  • @jakehobrath7721
    @jakehobrath7721 11 місяців тому

    @blackpenredpen Can you please do a break down of the integral arctan(x)/x^3 dx? I’m fascinated by it.

  • @AnimalSyndicate
    @AnimalSyndicate 10 місяців тому

    I f**ing love this guy!