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: Partial derivative chain rule question

  1. Nov 17, 2007 #1
    1. The problem statement, all variables and given/known data

    Given z= square root of xy, x = 2t - 1, y = 3t +4, use the chain rule to find dz/dt as a function of t.

    2. Relevant equations

    3. The attempt at a solution

    dz/dt = partial derivative of z with respect to x multiplied by dx/dt + (partial derivative of z with respect to y multiplied by dy/dt)

    I got that part right but how do you differentiate square root of xy as a partial derivative of z with respect to x?? Can you show me the final answer of that?

  2. jcsd
  3. Nov 17, 2007 #2
    take y as a constant and find the partial derivative of z=sqrt(xy) like you normally would.
  4. Nov 17, 2007 #3
    yea i tried that but could u give me the final answer to that particular part. would it 1/2x^-1/2 multiplied by y???
  5. Nov 17, 2007 #4
    you're missing a y with the x, it should be [tex]\frac{(xy)'}{2\sqrt{xy}}[/tex]

    where (xy)'=y

    when you take the partial derivative you're just leaving y as constant so the y stays with x under the square root.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook