Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: What is wrong with this differentiation?

  1. Jul 7, 2011 #1
    1. The problem statement, all variables and given/known data
    Find dy/dt, given:

    2. The attempt at a solution
    I am trying to use the chain rule for the case where y is a function of x, x is a function of s and s is a function of t, like below:
    But this gives (substituting x and s for their values as functions of t)
    which is not the correct result. The correct result is:
    What is wrong?

    Thank you in advance.
  2. jcsd
  3. Jul 7, 2011 #2
    Never mind. After doing some manipulations I found that apparently both results are equal, because these two terms of the answer given as correct:
    after some manipulation:
    become the two terms of the answer I found.
    Last edited: Jul 7, 2011
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook