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Thread: Problem With Integrating Factors

  1. #1
    Member billa's Avatar
    Joined
    Oct 2008
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    Problem With Integrating Factors

    SOLVED... You can ignore this ;D

    When I solve the following First-Order Linear ODE I get the wrong answer....

    $\displaystyle y' + y*tan(x)=sin(2x)$,$\displaystyle y(0)=1$

    I use the integrating factor $\displaystyle |sec(x)|$ and get the solution

    $\displaystyle y=k*|cos(x)|-2*cos^2 (x)$

    While a textbook and wolfram alpha say that there should be no absolute value sign around the cos(x)....

    I think my problem was in determining the integrating factor, can anyone explain what I did wrong? I used the formula $\displaystyle u=e^{\int tan(x) dx}$

    Thanks
    Last edited by billa; Feb 26th 2010 at 02:20 PM.
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