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Simple differentiation question

  1. Nov 13, 2014 #1
    Hey guys,
    Just a simple question to see if I'm going insane. So say I have an expression for:
    [tex]\frac{dxy}{dt} [/tex] and an expression for [tex]\frac{dy}{dt} [/tex], how to I go about isolating an expression for just [tex]\frac{dx}{dt} [/tex]
    I have tried using the product rule but it doesn't work for what I want. I know this is a very simple question but I haven't done calculus in a long time!
  2. jcsd
  3. Nov 13, 2014 #2


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    \frac{d(xy)}{dt}=\frac{dx}{dt}y+x\frac{dy}{dt}\Rightarrow \frac{dx}{dt}=\frac{1}{y}(\frac{d(xy)}{dt}-x\frac{dy}{dt})
  4. Nov 13, 2014 #3
    Yeah that's what I did.. I'm doing this in an ode solver in matlab so obviously my code is wrong elsewhere.
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