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Basic differential equation

  1. Nov 15, 2015 #1
    I have this basic differential equation du/dt=(u^2)*(sin t)

    This is obviously a separable diff eq.

    So what i've done is:

    g(t) = sin t h(u) = u^2

    1/(u^2) du = sin t dt

    Integrating both side....

    1/y = - cos t + c

    therefor y = - 1/(cos t + c)


    Which is wrong, there isn't supposed to be a minus sign apparently. I don't know what i've done wrong. Any suggestions? Thanks.
     
  2. jcsd
  3. Nov 15, 2015 #2

    pasmith

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    [itex]\frac{d}{du}(u^{-1}) = - u^{-2}[/itex], so you should have [tex]
    -\frac1u = -\cos t + c
    [/tex]

     
  4. Nov 15, 2015 #3
    Ah! Wow I'm so dumb haha, 3 hours sleep :D lol.

    Thanks a lot.
     
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