# Math Help - laplace sum

1. ## 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

2. ## Re: laplace sum

You don't need to use Laplace Transforms at all, simply solve the homogeneous equation and then apply the method of undetermined coefficients...

3. ## Re: laplace sum

Originally Posted by prasum
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