Thread: laplace sum

solve x''+9x=cos3t where x(0)=1 and x(pi/2)=-1

here x'(0) is not given and i am unable to use x(pi/2)=-1

please help!!

If you have to use Laplace Transforms, (there are other methods available), run the calculation through with x'(0) as an unknown constant. When you have your solution for x, substitute t=pi/2, x=-1 to evaluate the constant.