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ILIEKMATHPHYSICS
United States
Приєднався 12 бер 2014
Hello! I like to make videos on mathematical proofs and derivations!
Prove that sqrt(1+sqrt(1+sqrt(1+sqrt(...)))) = the golden ratio (ILIEKMATHPHYSICS)
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). For more details, see section 3.3 on the Monotone Convergence Theorem.
Thanks and enjoy the video!
Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
Thanks and enjoy the video!
Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
Переглядів: 1 009
Відео
Proof of the Intermediate Value Theorem (ILIEKMATHPHYSICS)
Переглядів 5014 години тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). The proof given in the book is different from the one we are doing in the video. We will do the approach done in the book in a future video, where we use method of bisections. Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_...
Prove using epsilon-delta: Limit of (2x^2 - 3x + 1)/(x^3 + 4) = 1/4 as x approaches 2
Переглядів 44712 годин тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). This exercise is not given in the book, but exercises related to it are given in Section 4.1. Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
If lim{x→ξ} f = η, lim{y→η} g = L, ξ ∈ I an open interval f(x) ≠η for all x ∈ I then lim{x→ξ} g∘f =L
Переглядів 28514 годин тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). This exercise is not in the book, but we give it here so that in the future, we make a video where we rigorously establish that the two common definitions of a derivative are equivalent. For more information related to this theorem, see proofwiki.org/wiki/Limit_of_Composite_Function. We are l...
Prove the limit of 1/sqrt(3x+7) = 1/5 as x approaches 6 (using epsilon-delta) (ILIEKMATHPHYSICS)
Переглядів 69819 годин тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). For more details related to the types of exercises covered in this video, see section 4.1. Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
Prove the limit of 1/(x^2 - 2) = -1 as x approaches 1 (using epsilon-delta) (ILIEKMATHPHYSICS)
Переглядів 1 тис.День тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). For more details regarding the type of problem in this video, see Section 4.1. Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
Prove if lim(xn+1/xn) ﹤ 1, then lim(xn) = 0 [ILIEKMATHPHYSICS]
Переглядів 1,2 тис.14 днів тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). This is given by Theorem 3.2.11 in the book. Here are the preliminary results we used in this video: Suppose (xn) is a sequence. If xn ≥ 0 for all n, then lim(xn) ≥ 0: ua-cam.com/video/6OwttPIjZKo/v-deo.htmlsi=BpsIz0zfloyz9Uvg Suppose 0 ﹤ b ﹤ 1. Then lim(b^n) = 0: ua-cam.com/video/V95RB0JMm9s...
Prove gcd(a,bc) = 1 if and only if gcd(a,b) = 1 and gcd(a,c) = 1 (ILIEKMATHPHYSICS)
Переглядів 31314 днів тому
This video is part of the "Intro to Higher Math" series I am making; it mainly references Daniel Velleman's book "How to Prove it" Third Edition. For more information, see Chapter 7. This exercise also appears in Chapter 0 of "Contemporary Abstract Algebra" by Joseph Gallian (Tenth Edition). We use Bezout's Lemma in this video. Here is a proof of this result: ua-cam.com/video/8eK94sl4Ouk/v-deo....
Suppose |A| = |B| are finite and f : A → B. Prove f is one-to-one iff f is onto (ILIEKMATHPHYSICS)
Переглядів 82014 днів тому
This video is part of the "Intro to Higher Math" series I am making; it mainly references Daniel Velleman's book "How to Prove it" Third Edition. For more information, see Chapter 8. We use some preliminary results in this video: At 1:26 we use: ua-cam.com/video/FR1Q9c68Mgk/v-deo.html At 2:10 we use: ua-cam.com/video/ZyYj5AwFEJQ/v-deo.html At 6:45 we use: ua-cam.com/video/NZhxuf4Fxos/v-deo.html...
Prove every bounded sequence has a convergent subsequence (The Bolzano-Weierstrass Theorem)
Переглядів 37021 день тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). The fact we are proving in this video is called the Bolzano-Weierstrass Theorem, and it is given as Theorem 3.4.8 in the book. See Section 3.4 for more details. Here are the two preliminary results we use in the proof: Prop (1): ua-cam.com/video/8OuLJSLF-DI/v-deo.html Prop (2): ua-cam.com/vid...
Prove that every sequence has a monotone subsequence (ILIEKMATHPHYSICS)
Переглядів 63021 день тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). The fact we are proving in this video is given by Theorem 3.4.7 and is called the Monotone Subsequence Theorem. Here is a proof of the result we use in the infinite case: ua-cam.com/video/WYjE8EB4eQ4/v-deo.html Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.c...
Proof of the Principle of Vacuous Truth (ILIEKMATHPHYSICS)
Переглядів 1,2 тис.28 днів тому
This proof is referenced from "An Introduction to Formal Logic" by forallx: Calgary. You can construct this proof yourself at: proofs.openlogicproject.org/. Here are the following preliminary results used in the proof: (i) Suppose Q. Then if P then Q. ua-cam.com/video/UmouLA3b1FA/v-deo.html (ii) The Contrapositive Law. ua-cam.com/video/JlUrs_Tcf_Q/v-deo.html Thanks and enjoy the video!
Prove that the limit of √(n+√n) - √n = 1/2 (ILIEKMATHPHYSICS)
Переглядів 1,8 тис.Місяць тому
This video references the book "Introduction to Real Analysis" by Bartle and Sherbert (Fourth Edition). For more details regarding the techniques used in this video, see Section 2.4 and Section 3.1. Thanks and enjoy the video! Real Analysis (Bartle and Sherbert) Playlist: ua-cam.com/play/PLDiddIbnOEOWLbdQ4DoC8bfaV_y4VyOsS.html
Prove in any group, (ab)^-1 = b^-1*a^-1 (ILIEKMATHPHYSICS)
Переглядів 424Місяць тому
This video references "Contemporary Abstract Algebra" by Joseph Gallian (Tenth Edition). For more information regarding the details of this video, see chapter 2. The fact in this video is sometimes called the socks-shoes property. Here is a proof of the preliminary result: ua-cam.com/video/zoggdnoxJak/v-deo.html Thanks and enjoy the video! Abstract Algebra Playlist: ua-cam.com/play/PLDiddIbnOEO...
Prove in any group, if ab = e then a = b^-1 and b = a^-1 (ILIEKMATHPHYSICS)
Переглядів 253Місяць тому
This video references "Contemporary Abstract Algebra" by Joseph Gallian (Tenth Edition). For more information regarding the details in this video, see chapter 2. Thanks and enjoy the video! Abstract Algebra Playlist: ua-cam.com/play/PLDiddIbnOEOVMsCFN5Gx10XMl9wD9t9LT.html
Proof of the Sequential Criterion for Limits of a Function (ILIEKMATHPHYSICS)
Переглядів 314Місяць тому
Proof of the Sequential Criterion for Limits of a Function (ILIEKMATHPHYSICS)
Proving the "division algorithm" for real numbers (ILIEKMATHPHYSICS)
Переглядів 347Місяць тому
Proving the "division algorithm" for real numbers (ILIEKMATHPHYSICS)
Prove that every group element has a unique inverse (ILIEKMATHPHYSICS)
Переглядів 371Місяць тому
Prove that every group element has a unique inverse (ILIEKMATHPHYSICS)
Prove that the left and right cancellation laws hold for groups (ILIEKMATHPHYSICS)
Переглядів 318Місяць тому
Prove that the left and right cancellation laws hold for groups (ILIEKMATHPHYSICS)
Prove that the limit of a function is unique (ILIEKMATHPHYSICS)
Переглядів 561Місяць тому
Prove that the limit of a function is unique (ILIEKMATHPHYSICS)
Prove if n is an integer ﹥ 1 then the nth root of n is irrational (ILIEKMATHPHYSICS)
Переглядів 1,9 тис.Місяць тому
Prove if n is an integer ﹥ 1 then the nth root of n is irrational (ILIEKMATHPHYSICS)
Prove that the nth root of a positive integer is either a positive integer or irrational
Переглядів 1,1 тис.Місяць тому
Prove that the nth root of a positive integer is either a positive integer or irrational
Prove if a^n divides b^n, then a divides b (ILIEKMATHPHYSICS)
Переглядів 579Місяць тому
Prove if a^n divides b^n, then a divides b (ILIEKMATHPHYSICS)
Prove if gcd(a,b) = 1 then gcd(a^n,b^n) = 1 [ILIEKMATHPHYSICS]
Переглядів 465Місяць тому
Prove if gcd(a,b) = 1 then gcd(a^n,b^n) = 1 [ILIEKMATHPHYSICS]
Prove that every rational number has exactly one simplest form (positive rationals)
Переглядів 463Місяць тому
Prove that every rational number has exactly one simplest form (positive rationals)
Prove if a prime p divides a1a2...an, then p divides some ai (ILIEKMATHPHYSICS)
Переглядів 423Місяць тому
Prove if a prime p divides a1a2...an, then p divides some ai (ILIEKMATHPHYSICS)
Prove that ab = gcd(a,b) ⋅ lcm(a,b) for positive integers a and b [ILIEKMATHPHYSICS]
Переглядів 853Місяць тому
Prove that ab = gcd(a,b) ⋅ lcm(a,b) for positive integers a and b [ILIEKMATHPHYSICS]
Proof of the Monotone Convergence Theorem (ILIEKMATHPHYSICS)
Переглядів 490Місяць тому
Proof of the Monotone Convergence Theorem (ILIEKMATHPHYSICS)
Prove if pn is the nth prime, then pn+1 ≤ p1p2...pn + 1 (ILIEKMATHPHYSICS)
Переглядів 829Місяць тому
Prove if pn is the nth prime, then pn 1 ≤ p1p2...pn 1 (ILIEKMATHPHYSICS)
Prove if |b| ﹤ 1 then lim(b^n) = 0 [ILIEKMATHPHYSICS]
Переглядів 1,6 тис.Місяць тому
Prove if |b| ﹤ 1 then lim(b^n) = 0 [ILIEKMATHPHYSICS]
🎉🎉🎉🎉🎉🎉 thank you very much for your beautiful work!!!!!!
Great video man. Thanks for being that organized, it has been really helpful for me :)
Can i get a link to the video for the result that you used!
yep, here it is For all x ≥ 0, there exists n ﹥ 0 such that n-1 ≤ x ﹤ n (Proof) [ILIEKMATHPHYSICS] ua-cam.com/video/7YYRElDIl-0/v-deo.html
Keep it up bro, this is very good. The way you explain is just different from every math's related youtubers
Haha that's a massive premise for an if -> then proof
To prove the fact that it's increasing, use proof by induction... Base case: x1 = 1, x2 = sqrt(2), so x2 > x1. Easy base case. Inductive case: Assume x(n) > x(n-1). Then 1 + x(n) > 1 + x(n-1). Therefore, sqrt(1 + x(n)) > sqrt(1 + x(n-1)). Therefore x(n+1) > x(n). Inductive case done.
Nice
I just love these! every singe step clearly explained! :))
:)
Also please prove the extreme value theorem.
Ok, this is going to be an adventure
can you show how to prove that the inverse of a bijective function is bijective
great resolution. hug from Brazil
Uraaaaaa ! Thank you so much for your detailed video analysis on this topic which is geometrically explained . I have thought that I will have to memorise this topic without understanding but you have come as a saviour before my engineering mechanics exam . Thanks again . A big cheers to your nice work .
idk whats going on but nice explaining man
I think that's the greatest title of a UA-cam video I've ever seen!
ikr it's so good 😊 it took me like 15-30 minutes to write a title
What is the point in still using an Epsilon Delta proof? Is there any instance in which it would be more efficient, because from what I’ve seen/know it only seems to complicate the proof.
Superb explanation brother. By the way,where do you live???? I am watching you from India 🇮🇳❤❤❤❤❤❤
How convenient that you got a |x-6|. If you had had, say |x-9| you would do |x - 6 -3| and apply triangle inequality to x - 6 and 3?
Getting cold?
lol i like how you knew that
It can be done more easily. The function f(x)=1/sqrt(3x+7) is obviously continuous in a neighbourhood of 6. But then lim_{x->6}f(x) = 1/sqrt(3(lim_{x->6})+7) = 1/sqrt(3*6+7)=1/5. The argument relies on the fact that lim_{x->y}f(x) = f(lim_{x->y}x) when f i contiuous at y.
So you're proving a prerequisite for continuity by assuming continuity? Obviously if we "know" that f is continuous at 6 we can just evaluate the function at x=6, the catch is you've got to prove it first :S
@@mattikemppinen6750 Draw the graph of f near 6. You can do it without lifting the pencil. So it's continuous. That's basic highschool math.
haha nice. Just getting into proofs and i love your channel
@@Artemis88446 I'm MSc Mathematics, and everything he does i highly rigorous. You can trust this man.
Thank you
I am doing Calculus and hope I don't have to do this in the exam. Anyway it's really interesting
I think I'm gonna do another one of these exercises as my next video
Im sorry you think that.
support
I really like how you make sure these videos are easy to understand for everybody by explaining every step. Which means if it's a really hard problem I can trust that I will understand it with your explanations.
Can't you figure out the fact that it's a geometric series and say x_(n+1)/x_n=L where 1>L>0. Then you say L(x_n)=x_(n+1) and since L is between 1 and 0 that means the function of x_n is decreasing exponentially and is approaching 0 as n--->infinite.
Cool approach of induction on n for all n≥m≥1 with fixed m
Is there a generalization example of that induction but for real number x instead of natural number m i.e., ∀n∈ℕ ∀x∈ℝ (n≥x≥0⇒P(n,x))? Mabe using floor/ceil(x)?
Keep it up homie. I’m glad you’re so consistent bc it really helps me out sometimes, and it’s just cool stuff!
I believe this result is used in calculus for convergence of sequences all the time. Nice to see a proof of it.
I like how you outline the proof so that this sketch can be generalised. Love your videos!
Awesome ❤
I really needed this
Great content brother 🗿
This is a spectacularly well-explained and reasoned-through video. Bravo.
Nice
Great ❤
For the second part, you can use Bezout lemma and don't have to go back to the definition of gcd. Suppose gcd(a, b) = 1 and gcd(a, c) = 1. Step 1. a * p + b * q = 1 for some p, q in Z Step 2. a * r + c * s = 1 for some r, s in Z Want: a * x + (b * c) * y = 1 for some x, y in Z Step 3. a * c * p + b * c * q = c by multiplying step 1 by c Step 4. a * c * p * s + b * c * q * s = c * s by multiplying step 3 by s Step 5. a * c * p * s + b * c * q * s = 1 - a * r from steps 4 and 2 Step 6. a * (c * p * s + r) + (b * c) * (q * s) = 1 from step 5 Hence gcd(a, bc) = 1 by Bezout lemma
I am enjoying Your videos. Whenever I get time, I come here and just look into the statements and I try to prove myself. Helps me a lot in maintaining my form.
And for infinite sets?
This doesn't hold
I just want to say that this is so descriptive compared to other videos. Thank you!
sqrt((n)+sqrt(n))-sqrt(n)=(sqrt((n)+sqrt(n))-sqrt(n))*(sqrt((n)+sqrt(n))+sqrt(n))/(sqrt((n)+sqrt(n))+sqrt(n))=(n+sqrt(n)-n)/(sqrt((n)+sqrt(n))+sqrt(n))=sqrt(n)/(sqrt((n)+sqrt(n))+sqrt(n))=(sqrt(n)/sqrt(n))*1/(sqrt((1)+1/sqrt(n))+1)=1/(sqrt((1)+1/sqrt(n))+1) lim(1/(sqrt((1)+1/sqrt(n))+1)) x---> inf =1/(1+0+1)=1/2
I was dying for this solution 😢 THANKYOU SIR
amazing
Best explanation 😇
Another way to prove this would be to split the sequence to 2 cases: bounded and unbounded. If it is bounded, it would have a limit point and if it has a limit point, it would be easy to construct a monotone subsequence by adjusting epsilon appropriately. If it is unbounded on any one side, it is trivial to construct a monotone subsequence.
thank you
Something about this feels overly complicated. I'm a bit of an amateur (math-adjacent degree, but didn't get this far into formality). Let me see if I got this: If I have a sequence of *any* Real numbers (x_n), then I can pick out either a finite or (if available) an infinite number of elements of the sequence, in the order in which they appear in the original sequence, and in doing so, I can ensure that the elements that I choose have at least one of the following patterns: a) these still sequence-ordered elements are already in nonascending order, or b) these still sequence-ordered elements are already in nondescending order, or c) these still sequence-ordered elements are equal to each other (which counts as both nonascending and nondecreasing). Is that good common-wording understanding of this theorem? And if that's right, then it sounds like the Empty Sequence and single-element sequences (i.e.: single numbers) may be degenerate/trivial/vacuous cases, but then for any sequence of 2 or more elements, I can pick any 2 different-position elements, and either one must be greater than the other, or they must be equal to each other.
your common-wording understanding seems right, and in this theorem, we only care about infinite sequences of real numbers, so the sequence (xn) in this proof means the function x : Z+ --> R whose outputs are x_1, x_2, x_3, ..., x_n, ...; likewise subsequences are infinite
if the subsequence is allowed to be fiinite, it's even simpler than that. Pick the first two elements x1, x2 If x1 > x2, the subsequence {x1, x2} is a monotonic decreasing subsequence. If not, it's monotonic increasing. End of proof. Edit: Oh, I see that you included my example in your comment already.
Sequences and subsequences of real numbers, by definition, are functions from N to R. Thus, they have "infinitely many elements" In other words, tuples are not sequences, they are tuples. Sequences are, by definition, infinite