1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Chain rule find find dw/dt

  1. Oct 3, 2005 #1
    Suppose w = x/y + y/z

    x = exp(t), y=2+sin(5t), and z= 2+cos(7t)

    A.) Use the chain rule to find dw/dt as a function of x, y, z, and t. Do not rewrite x, y, and z in terms of t, and do not rewrite exp(t) as x. I got this one right, the answer is 1/y*exp(t) +(- x/y^2+1/z)*(5*cos(5t)) + (-y/z^2)*(-7sin(7t)).

    i need help on B.

    B.) Use part A to evaluate dw/dt when t=0
    i just plugged in zeros for t, but i get an answer with the variables y and z, which i shouldnt have. what am i suppose to do for this question?
  2. jcsd
  3. Oct 3, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Well x, y and z are functions of t aren't they? So when you set t=0, you've GOT to write x, y and z in terms of t, and then set t=0 in the resulting equation.
  4. Oct 3, 2005 #3
    yup, thanks alot
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook