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Homework Help: Using chain rule to obtain the derivative dz/dt

  1. Nov 3, 2015 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    dz/dt = dz/dx⋅dx/dt + dz/dy⋅dy/dt

    3. The attempt at a solution

    I am getting :

    =[-sin(x+7y) ⋅ 10t] + [-sin(x+7y) ⋅ 7 ⋅ (-1/ t2)]

    then changing x and y terms:

    =[-sin((5t2)+7(1/t)) ⋅ 10t] + [-sin((5t2)+7(1/t)) ⋅ 7 ⋅ (-1/ t2)]
  2. jcsd
  3. Nov 3, 2015 #2

    Ray Vickson

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    Do you have a question?
  4. Nov 3, 2015 #3
    yes, sorry, I'm just verifying If I had done it correctly.
    the answer my teacher posted was :
    which really got me questioning myself.
  5. Nov 3, 2015 #4


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    Science Advisor
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    It seems that you teacher has ##x(t)=5t^4##
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