Results 1 to 9 of 9

Math Help - Derivatives

  1. #1
    Newbie
    Joined
    Oct 2010
    Posts
    5

    Derivatives

    find the dy/dx of y=4(sec x+ tan x)^1/2, idk how to put root...
    please help me i don't know what to do
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
     4(sec x+ tan x)^{1/2} = 4 \sqrt{sec(x)+tan(x)}

    Use the Chain Rule.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2010
    Posts
    5
    I know i need to use Chain Rule but i don't know how!!!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie Tatsuya's Avatar
    Joined
    Oct 2010
    From
    Washington
    Posts
    6
    I'm no expert at this (posted a chain rule question yesterday actually) but I think you want to take dy/du of 4u^1/2 and du/dx of u=(sec x + tan x) and multiply. Then substitute (sec x + tan x) back into the equation for u.

    I'll stick around for the answer to this question because I'm not confident in my work. When I try to solve I get an ugly answer, which may be true...but I'm not sure.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Senior Member Educated's Avatar
    Joined
    Aug 2010
    From
    New Zealand
    Posts
    424
    Thanks
    11
    Chain rule:

    (f \cdot g)'(x) = f'[g(x)] \cdot g'(x)

    Leave the function as a power y= 4 (\sec x+ \tan x)^{1/2} and let \sec x+ \tan x = g(x)

    Can you show us your attempt at it?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member
    Joined
    Mar 2010
    Posts
    715
    Thanks
    2
    \displaystyle \left(\sqrt{f(x)}\right)' = \frac{f'(x)}{2\sqrt{f(x)}}
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Oct 2010
    Posts
    5
    i don't understand what is the derivative of y=4(sec x+ tan x)^1/2.............................
    is it 7/2(secx+tanx)^-1/2??? pretty much this is why iam asking this question..
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by kevinoh92 View Post
    i don't understand what is the derivative of y=4(sec x+ tan x)^1/2.............................
    is it 7/2(secx+tanx)^-1/2??? pretty much this is why iam asking this question..
    differentiate 4Sqrt[(1/Cos[x]+ Tan[x]] - Wolfram|Alpha

    Click on Show steps.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    Oct 2010
    Posts
    5
    Thanks ,mr fantastic
    Last edited by mr fantastic; October 25th 2010 at 03:33 AM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Derivatives and Anti-Derivatives
    Posted in the Calculus Forum
    Replies: 7
    Last Post: February 6th 2011, 06:21 AM
  2. Replies: 1
    Last Post: July 19th 2010, 04:09 PM
  3. Replies: 4
    Last Post: February 10th 2009, 09:54 PM
  4. Trig derivatives/anti-derivatives
    Posted in the Calculus Forum
    Replies: 1
    Last Post: February 10th 2009, 01:34 PM
  5. Second derivatives
    Posted in the Calculus Forum
    Replies: 3
    Last Post: October 3rd 2008, 02:09 PM

Search Tags


/mathhelpforum @mathhelpforum