# Laplace transform

1. Oct 2, 2012

### ensten

1. The problem statement, all variables and given/known data

Find f(t) for:

$2\int_{0}^{t}f'(u)sin(9(t-u)du +5cos(9t), t\geq0$

3. The attempt at a solution

$F(s)=2\frac{9(sF(s)-f(0))}{s^2+81}+\frac{5s}{s^2+81}$

At this point i don't know what to do with f(0) since there are no initial conditions.
What do I do with it?

2. Oct 2, 2012

### vela

Staff Emeritus
It's just a constant that'll appear in your final answer. You'll have a term proportional to f(0).