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Math Help - Partial derivatives

  1. #1
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    Partial derivatives

    Suppose u = x^4*y + y^2*z^3, where x = r*s*e^t, y = r*s^2*e^-t, and z = sin(t)r^2*s. Find du/ds.
    So I believe you plug in x, y, and z into the equation to get:
    u = (rse^t)^4*(rs^2e^-t) + (rs^2e^-t)^2*(sin(t)r^2s)^3
    And I know you have to treat all the variables except s as a constant, but I'm just getting confused with all the numbers. Thanks!
    Last edited by tbl9301; September 9th 2009 at 07:56 PM.
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  2. #2
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    Hi tbl9301

    If so, then just change all the other variables to simple ones.
    1. re^t --------> A
    2. re^(-t) -----> B
    3. sin(t) r^2 --> C

    Then you have :

    u = (As)^4 * (Bs) + (Bs)^2 + (Cs)^3
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  3. #3
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    that helps a lot thank you!
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  4. #4
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    You're welcome
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