Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

core 3 differentiation differentiate tan^2y pls help watch

    • Thread Starter
    Offline

    21
    ReputationRep:
    Name:  ImageUploadedByStudent Room1447348480.994720.jpg
Views: 214
Size:  109.7 KB pls help me with part a....I tried quotient rule but I'm still not getting the answer


    Posted from TSR Mobile
    • Very Important Poster
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by bubblegumcat)
    Name:  ImageUploadedByStudent Room1447348480.994720.jpg
Views: 214
Size:  109.7 KB pls help me with part a....I tried quotient rule but I'm still not getting the answer


    Posted from TSR Mobile
    Are you given the derivative of y = arctan(x)?
    Offline

    7
    ReputationRep:
    Are there any other rules of differentiation you can think of that may help?
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by SeanFM)
    Are you given the derivative of y = arctan(x)?
    do I need to know that? I was never taught that :s


    Posted from TSR Mobile
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by lukejoshjames)
    Are there any other rules of differentiation you can think of that may help?
    I tried dy/du x du/dx(I think that's correct) and I got 2tanysec^2y but I'm not sure if that's right


    Posted from TSR Mobile
    • Very Important Poster
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by bubblegumcat)
    do I need to know that? I was never taught that :s


    Posted from TSR Mobile
    Oh, don't worry about then

    It may help to find dx/dy using the chain rule and see where that gets you.

    (Original post by bubblegumcat)
    I tried dy/du x du/dx(I think that's correct) and I got 2tanysec^2y but I'm not sure if that's right


    Posted from TSR Mobile
    There you go - so what does that equal to? And how do you get x back into the equation?
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by SeanFM)
    Oh, don't worry about then

    It may help to find dx/dy using the chain rule and see where that gets you.
    oh i tried that I think...2tan y sec^2y is what I got..I'm not sure if that's correct?


    Posted from TSR Mobile
    • Very Important Poster
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by bubblegumcat)
    oh i tried that I think...2tan y sec^2y is what I got..I'm not sure if that's correct?


    Posted from TSR Mobile
    Correct so far :borat: - now see my edit in the post above.
    Offline

    22
    ReputationRep:
    (Original post by bubblegumcat)
    oh i tried that I think...2tan y sec^2y is what I got..I'm not sure if that's correct?


    Posted from TSR Mobile
    What trigonometric identity relates \sec^2 y and \tan^2 y?
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by Zacken)
    What trigonometric identity relates \sec^2 y and \tan^2 y?
    1 +tan^2 = sec^2?


    Posted from TSR Mobile
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by SeanFM)
    Oh, don't worry about then

    It may help to find dx/dy using the chain rule and see where that gets you.



    There you go - so what does that equal to? And how do you get x back into the equation?
    that would be 2tany/cos^2y right ?


    Posted from TSR Mobile
    Offline

    22
    ReputationRep:
    (Original post by bubblegumcat)
    1 +tan^2 = sec^2?


    Posted from TSR Mobile
    No. 1 + \tan^2 y = \sec^2 y
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by Zacken)
    No. 1 + \tan^2 y = \sec^2 y
    how does that relate to this question? do I need to change tan^2y into sec^2y-1?


    Posted from TSR Mobile
    • Very Important Poster
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by bubblegumcat)
    that would be 2tany/cos^2y right ?


    Posted from TSR Mobile
    That is still dx/dy but you've changed sec into cos, which can work but you don't need to do it.

    Remember that dx/dy = 1/(dy/dx).

    As Zacken is helping as well I will bow out. :hat2:
    Offline

    22
    ReputationRep:
    (Original post by bubblegumcat)
    how does that relate to this question? do I need to change tan^2y into sec^2y-1?


    Posted from TSR Mobile
    No. You know that \tan^2 y = x and you want an answer involving x so you want to convert everything into \tan^2 y.
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by SeanFM)
    That is still dx/dy but you've changed sec into cos, which can work but you don't need to do it.

    Remember that dx/dy = 1/(dy/dx).

    As Zacken is helping as well I will bow out. :hat2:
    ohhh I see, thanks!


    Posted from TSR Mobile
    • Thread Starter
    Offline

    21
    ReputationRep:
    (Original post by Zacken)
    No. You know that \tan^2 y = x and you want an answer involving x so you want to convert everything into \tan^2 y.
    got it, thanks!


    Posted from TSR Mobile
    Offline

    22
    ReputationRep:
    (Original post by bubblegumcat)
    got it, thanks!


    Posted from TSR Mobile
    Thank SeanFM. :-)
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 12, 2015
Poll
Do I go to The Streets tomorrow night?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.