1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Solving a derivative

  1. Jul 18, 2012 #1
    1. The problem statement, all variables and given/known data
    Find the derivativce of y=e^cosx*sinx

    2. Relevant equations



    3. The attempt at a solution

    i`m just unsure of whether e should be treated as e^x because its not that.. or if e should be treated like an f(x)a^x to f`(x)a^xlna, or if it is still considerd e^x.. here is my attempt.

    y`=e^cosx*(-sinx)*(sinx) + (cosx)(e^cosx)

    y`= e^cosx(cosx - sin^2x)
     
  2. jcsd
  3. Jul 18, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member


    If you're differentiating y = (sin(x))ecos(x), then what you have done is fine.

    Writing ax as ex ln(a) can be helpful at times, but writing e in terms of some other constant generally isn't helpful when differentiating.
     
  4. Jul 18, 2012 #3

    Ah i just realised something... e^x = e^cosx in the sense that cosx is `x`. right?

    And also thank you for your help.
     
  5. Jul 18, 2012 #4

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The chain rule. ##(f\circ g)'(x)=f'(g(x))g'(x)##
    The product rule. ##(fg)'(x)=f'(x)g(x)+f(x)g'(x)##


    Keep in mind that ##e^{f(x)}=exp(f(x))=(\exp\circ f)(x)##. So you will need the chain rule. You will also need the product rule to find f'(x).
     
  6. Jul 18, 2012 #5
    all right, thanks man.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Solving a derivative
  1. Solving Derivatives (Replies: 1)

  2. Solving derivative (Replies: 3)

Loading...