Variation of Parameters

  • Thread starter jrsweet
  • Start date
  • #1
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Homework Statement


Find a particular solution to:

y''+4y=20sec(2t)


Homework Equations





The Attempt at a Solution


y''+4y=0
r^2+4=0
r=+or- 2i

So, yc(t) = Asin(2t) + Bcos(2t)
yp(t)= -cos(2t) ∫ 10sin(2t)sec(2t)dt + sin(2t) ∫ 10cos(2t)sec(2t)dt
= -10cos(2t) ∫ tan(2t)dt+10sin(2t) ∫ 1dt
= -10cos(2t)(-.5ln(cos(2t)))+10tsin(2t)

I don't know what's wrong. Can anyone help me out?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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I don't know if you did it in your integrands but did you happen to divide R(x)y1(x) by W(y1,y2) where W is the wronskian ?
 

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