var('x,y')
y=function('y',x)
desolve(diff(y,x,2) + 9*y == cos(3*x), dvar = y) # i have assumed that the trig angle is cosine

SageDays/Kreyszig-2.11-4 (last edited 2010-08-11 13:11:44 by Abhi-akash)