Integration help

  • #1
howdy, i uhh solved this problem early in the semester, and now im looking at it like wtf did i do to get the right answer....it says use the 'off the shelf formula' for first order diff eqns.

its pretty much just integrating now

y(x) = e^(x) (int[e^(-x)*-sin(2x)dx] + c)

ans => y(x)= 1/5(sin2x-2cos2x)+c

thanks in advance
 

Answers and Replies

  • #2
berkeman
Mentor
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Are you sure you transcribed those correctly? What do you get when you differentiate the answer you've listed? Just sin and cos terms, right?
 
  • #3
1,235
1
If [tex] y(x) = e^{x}\int e^{-x}\times -\sin 2x \; dx [/tex]
 
  • #5
1,235
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use integration by parts.
 
  • #6
HallsofIvy
Science Advisor
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Ignore the ex outside the integral until you have done the integral itself, using integration by parts (twice) as courtigrad said. (Presumably the integration will have a factor of e-x, canceling the ex outside the integral.)
 

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