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    Hi - i'm new to this forum so bar with me if my formatting is off

    I have quite a simple second order ODE but it's been a while...

    y''+3y'+2y=5sinx

    first i found the CF

    L^2 + 3L + 2 = 0

    => y = Ae^-2x + Be^-x

    now i need to find the PI...

    is it a simple case of setting y=Csinx then subbing into my original equation? when i do that i get cos terms which are hard to lose :s

    any help would be good thanks
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    Csinx+Dcosx if the thing you want to end up with is of the form sinx or cosx.
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    Particular integral in the case of sin or cos needs to be

     C cosx + D sin x

    That might work out a little nicer with the algebra...
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    ^ wait i think i've got it.

    do i set y=Dsinx + Ccosx?

    that gets me D=-5/8 C=15/8

    then add PI and CF to get y(total)?

    EDIT:thanks guys - i hadn't learnt the joys of refresh yet
    EDIT2: does this forum support tex?
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    Hey Boltman, yeh it does support tex (by which I assume you mean LaTeX ;D)

    Example:

    Solve for y
    \displaystyle\frac{d^2y}{dx^2}+3  \frac{dy}{dx}+2y=5sinx


    Just the standard surround your LaTeX by [tex] tags, have a little look here ;D
 
 
 
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