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 Question

  1. Aug 9, 2017 #1
    I am having difficulty trying to figure the following .

    What is [tex] \frac{\mathrm{d} }{\mathrm{d} x}f(x,y) [/tex] where x is a function of s and t.

    Here is my calculation [tex] \frac{\mathrm{d} }{\mathrm{d} x}f(x(s,t),y) = \frac{\partial f}{\partial x}\frac{\partial x}{\partial t}+\frac{\partial f}{\partial x}\frac{\partial x}{\partial s} [/tex]

    Does this seem correct?
  2. jcsd
  3. Aug 9, 2017 #2


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    That seems wrong. df/dx is just the change of f per unit change of x. It doesn't matter that x is a function of s and t. Once you figure out what df/dx is and you want to evaluate it at some value of x, then you can worry about x being a function of s and t.

    PS. f is actually a function of both x and y, so it is a partial derivative on the left ∂f/∂x.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted