dsolve('D2x+0.5*Dx+9*x=2*sint','t')
ans =
exp(-1/4*t)*sin(1/4*143^(1/2)*t)*C2+exp(-1/4*t)*cos(1/4*143^(1/2)*t)*C1+2/9*sint
少了个t
dsolve('D2x+0.5*Dx+9*x=2*sint','t')
ans =
exp(-1/4*t)*sin(1/4*143^(1/2)*t)*C2+exp(-1/4*t)*cos(1/4*143^(1/2)*t)*C1+2/9*sint
少了个t