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!

Partial Derivative Question

  1. May 16, 2012 #1
    1. The problem statement, all variables and given/known data
    If f(x,y) = x(x^2+y^2)^(-3/2)*e^(sin(x^2y)) find the derivative of f with respect to x at the point (1,0).


    3. The attempt at a solution
    The textbook solution just plugs 0 into y and gets f(x) = x^-2 and then proceeds to differentiate this resulting in the answer -2. I don't understand why this is legal. How can you just plug the point into the function and then take the derivative?

    For example, if I had the function y = x and I wanted the derivative at x=0. You can't just plug in zero and take the derivative...?
     
  2. jcsd
  3. May 17, 2012 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Because when you taking a partial derivative of a function of two variables f(x,y) with respect to x you assume y is a constant. You can either find it for any y or plug in a value for y to being with. y=x isn't a function of two variables.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Partial Derivative Question
Loading...