Using sum and difference formula to find the exact value with cosine

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  • Опубліковано 16 лис 2024

КОМЕНТАРІ • 96

  • @amasterofone
    @amasterofone 3 роки тому +102

    Dude, I'm in college Trig right now and I am STRUGGLING. My professor doesn't explain the logic behind anything and the textbook videos aren't much better. Your videos are the reason I've understood most of what has been taught in the class. I can't thank you enough.

    • @huntersage4007
      @huntersage4007 Рік тому +1

      exact same boat

    • @DrPeppaa
      @DrPeppaa Рік тому

      @@huntersage4007 same lol. Should not have taken it online!

    • @cesareoespinoza5642
      @cesareoespinoza5642 Рік тому +3

      Bro I’m in high school taking this😭😭

    • @ethanhayes3584
      @ethanhayes3584 Рік тому

      @@DrPeppaa I feel that! Test in an hour :(

    • @DrPeppaa
      @DrPeppaa Рік тому +1

      @@ethanhayes3584 best of luck to you brother, hope you passed 👍🏽

  • @ModanoTheBest
    @ModanoTheBest 5 років тому +216

    That feeling when he uses the exact problem you've been given. 🥰

    • @camp1158
      @camp1158 3 роки тому +5

      ergo when your teacher is just as lazy as you are :D (you impersonal)

    • @calthekonqueror312
      @calthekonqueror312 11 місяців тому +1

      Never have I more related to a 4 year old comment

    • @elliottgarneau
      @elliottgarneau 7 місяців тому +1

      SAME

  • @abrahamwashington3896
    @abrahamwashington3896 5 років тому +17

    For anyone wondering how he got the (pi/3 + pi/4)
    How I got it is pick a point on the unit circle, such as pi/3 or pi/4 (it helps to memorize the unit circle) and minus that by 7pi/12.
    So I'll pick pi/4 because from memorizing the unit circle I know that we can subtract and get the 2nd value
    1.) 7pi/12 - pi/4
    1a.) pi/4 -> becomes 3pi/12 we need equal denominators to subtract from 7pi/12
    2.) 7pi/12 - 3pi/12 = 4pi/12
    2a.) simply 4pi/12 and you get pi/3
    3.) you can verify that the values
    pi/4 pi/3 and by adding both and you will get 7pi/12
    I appreciate brian Logan saying not to worry about getting the 2 sums or difference to get the ball rolling but eventually this will catch up with you and you will have a gap in your knowledge. I can't think intuitively like that in math so I find this sort of algorithmic way to find the values.

  • @ZJasmineDragon
    @ZJasmineDragon 6 років тому +219

    There are no bad questions from someone whose never seen it, wish he didn't sorta snub her, that deters people from asking questions in the future

    • @brianmclogan
      @brianmclogan  6 років тому +134

      great point, I always welcome questions from students, not sure the context of this lesson or question. Sometimes when I notice students not paying attention but then asking questions when everyone else was paying attention knows, I get frustrated. Not sure if that was the case, or I could have just had a bad day.

    • @lucasargandona4658
      @lucasargandona4658 6 років тому +25

      Happens to the best of us

    • @kyleallen6809
      @kyleallen6809 5 років тому +15

      it was a stupid question anyway

    • @SurvivingAnotherDay
      @SurvivingAnotherDay 5 років тому +3

      @@lucasargandona4658 oh yeah yeah

    • @tha_oz
      @tha_oz 5 років тому +22

      yeah that was why I sucked at math in hs and middle school... too afraid to ask questions cuz I didn't want to get called out on

  • @kennybutcher6307
    @kennybutcher6307 Рік тому +4

    I sat in my chair for 3 hours trying to figure this out.. 1:35 ... holy crap! Thanks!

  • @KingdomTalkMinistry
    @KingdomTalkMinistry 5 років тому +101

    lol nooo dont loose your patience with that person. i needed that answer example ti finish my homework lol.

  • @coolguy3513
    @coolguy3513 Рік тому +2

    Exam tomorrow and you helped me understand this type of problem thank you 😅😅

  • @rawonion3591
    @rawonion3591 7 місяців тому

    in 10th grade in highschool and my teacher in algebra 2 sucks. this dude helps so much. i know this is 8 years later, but thank you 🙏🙏

  • @AA-sx9xu
    @AA-sx9xu 7 років тому +43

    He is a wonderful prof, makes life easy. Makes solving math problems piece of cake :)

  • @the_epic_medic299
    @the_epic_medic299 3 роки тому +1

    THIS MAN IS A GIFT FROM GOD BLESS YOU GOOD SIR

  • @michaelahulsey5085
    @michaelahulsey5085 6 років тому +8

    Found the video on radians! Great job! Im not sure if you are a teacher or professor, but either one you teach very well!! 😬😅

  • @user-bp4qq7tt1u
    @user-bp4qq7tt1u 4 роки тому +17

    im curious what level you are teaching at?? i wish my professor would be this thorough on explanations but we're always strapped for time.. she just seems to blaze through topics.. and right as i make sense of it, she moves to the next topic. I
    really appreciate all the effort and time it took to make this channel tho .. youve helped me immensely in my trig class.. ​ Brian McLogan

    • @Crusty_the_goblin
      @Crusty_the_goblin 2 роки тому

      I'm learning this in dual credit highschool, so college level maybe?

    • @pierce2928
      @pierce2928 2 роки тому +1

      Highschool level

  • @caleblong6106
    @caleblong6106 4 роки тому +15

    Why am I a junior in high school learning this 🥺

  • @sadiaaa1373
    @sadiaaa1373 2 роки тому

    Heres an easy way to find the two additions if you have to:
    If you had 7pi/12 like in this example, just do
    Api/12 + Bpi/12 = 7pi/12
    You have to find numbers that are divisible by 12 that also add upto 7, so its a bit of mental math here but its never too bad
    I know 2pi/12 and 5pi/12 add upto 7pi/12 but 5pi/12 *isnt divisible by 12* so dont use that pair.
    I know that 3pi/12 and 4pi/12 equal 7 and both numbers are also divisible by 12 so it works.
    Simplify and you get pi/4 and pi/3 which are your special triangles and useful for finding exact values

  • @simpforme.
    @simpforme. 6 років тому +2

    you're a lifesaver !! thank you so much

  • @kendall9298
    @kendall9298 2 роки тому

    How will you do cos(Pi/16) ? It’s a decimal value so it isn’t on the unit circle

  • @jakegrinnell7877
    @jakegrinnell7877 Рік тому

    Thank you!

  • @pickle2696
    @pickle2696 9 місяців тому

    زۆر سوپاس مامە گیان، ڤیدیوێکی بەسوودە

  • @hanzradjaie2109
    @hanzradjaie2109 4 роки тому +1

    What if it is negative? Cos-(7π/12)?

  • @MunshyaBW
    @MunshyaBW 6 років тому +3

    Can we convert that from rad to degrees and solve using trig sum or difference formulas??
    Say: cos(60 + 45) = cos60cos45 + sin60sin45 and then use the special triangles??
    My test is tomorrow so you probably wont see this on time :)

    • @kinghassy334
      @kinghassy334 6 років тому +2

      That's what he did but his trials are in radians

  • @eliashatescomm
    @eliashatescomm 7 років тому

    YOU MAKE IT EASIER! THANK YOU SO MUCH!

  • @zechvassar5508
    @zechvassar5508 5 років тому +4

    I still dont get it

  • @chloeblack9641
    @chloeblack9641 4 роки тому

    can you show how to solve it by converting to degrees please?

  • @marcus3435
    @marcus3435 5 років тому +2

    is there a way to memorize the subtraction/addition formulas for sin/cos/tan?

    • @brianmclogan
      @brianmclogan  5 років тому +11

      write them a lot

    • @d.9872
      @d.9872 5 років тому +5

      Brian McLogan 😂😂😂😂😂😂

  • @mirabudathoki7699
    @mirabudathoki7699 4 роки тому

    Thanks for this but plz make a video of sin2 360.

  • @vishalmishra3046
    @vishalmishra3046 Рік тому

    Lot of videos on easy problems. Why no video on hard problems - e.g. how to calculate sin π/17 ?

  • @veronicapereyra8329
    @veronicapereyra8329 4 роки тому +2

    why did the sign chage though?

    • @redangrybird7564
      @redangrybird7564 4 роки тому

      The sin identity gets to keep the same sign, but for the cosine the sign changes, that's the way it is but i don't know the reason.

  • @k12becgr62
    @k12becgr62 6 місяців тому

    I think your pi/3 should be 3pi/8 and your pi/6 should be pi/8 in your sketch.

  • @nathan_kul3152
    @nathan_kul3152 7 років тому

    Didn't understand where the addition terms came from and you helped me big time

  • @jurimessenbock3723
    @jurimessenbock3723 6 років тому

    its actually 105 degrees, not 95 degress as he said

  • @MunshyaBW
    @MunshyaBW 6 років тому +1

    Never mind it works

  • @muafenlor7015
    @muafenlor7015 6 років тому +2

    I got scared bc he said my name when he did the U and V bc i dont do them lol.

  • @Raaqiyaabshirahmed
    @Raaqiyaabshirahmed 2 роки тому

    Plzzz sin 2tita÷5

  • @pinkykumari5713
    @pinkykumari5713 3 роки тому +1

    India

  • @TheHunkOfHamburg
    @TheHunkOfHamburg 3 роки тому +2

    you lost me at the start

  • @Chuckiey
    @Chuckiey 2 місяці тому

    One of the very few videos I’ve disliked. Most videos are more so for people as slow as I am, and there are an unusual amount of assumptions in this one. Assuming students catch on or follow you at the snap of a finger made me feel bad, as I’ve never really been good with math. But I am trying. Nonetheless, I still appreciate the attempt!

  • @inventing...3717
    @inventing...3717 5 років тому

    Eeeeyeaah next video

  • @rebeccarose6567
    @rebeccarose6567 7 років тому +1

    your thumbnail looks funny xD

  • @moviestoday6659
    @moviestoday6659 6 років тому +1

    Do you get paid extra for these videos?

    • @brianmclogan
      @brianmclogan  6 років тому +12

      nope just a little from the ads, I just love helping and hearing from students all over the world, makes everything worth it

    • @user-sl1ml
      @user-sl1ml 3 роки тому +1

      he has more views and subs than some people who do it full time i’m sure at least now he makes a lot off of it

  • @b3N0_jojo
    @b3N0_jojo 6 років тому +8

    im in 8th grade doing this

    • @SSJQ127
      @SSJQ127 6 років тому +7

      Kylestyle16 Im a senior in high school and I dont get this lol. Good Luck

    • @Mikecieslak1
      @Mikecieslak1 6 років тому +5

      im a freshman in college and I don't know what Im doing lmao

    • @DanielHernandez-xc6hw
      @DanielHernandez-xc6hw 5 років тому +1

      I’m a 11 grader and don’t get this 😂

    • @tyleraskelton10
      @tyleraskelton10 5 років тому +2

      I'm a junior in college studying this at 6am so best of luck to ya girl

  • @mayrarivera1145
    @mayrarivera1145 4 роки тому +1

    If I didn't have a clue of math, I probably wouldn't understand this teacher. Lmao! Just saying.

  • @suitedgamer9607
    @suitedgamer9607 4 роки тому

    Ha lol

  • @samuelfrancois3357
    @samuelfrancois3357 3 роки тому +1

    It seems like he have no patience and a nasty sarcasm. He should be happy someone is asking questions and wants to learn no matter how many times you've repeated it. My opinion.