。y" +y sin 2t , y(0) = 0 , y'(0) = 1。(15 分)
y’’+y=sin2t, y(0)=0, y’(0)=1
Laplace transform
s2Y-sy(0)-y’(0)+Y=1/(s2+22)
(s2+1)Y-1=1/(s2+22)
Y= [1/(s2+22) -1]/(s2+1)
= 1/(s2+22)(s2+1) -1/(s2+1)
= 1/3[-1/(s2+22)+ 1/(s2+1)] -1/(s2+1)
inverse Laplace transform
y(t)=1/3(-sin2t+sint)-sint
=-1/3sin2t-2/3sint