Laplace transform with Convolution

[NJJ289]

Homework Statement

Use convolution theorem to solve:

\mathfrak{L} \left \{t\int_{0}^{t} \sin \tau d\tau \right \}

Do not solve the integral.

Homework Equations

"Convolution Theorem" in textbook is stated as:

\mathfrak{L}\left \{ f*g \right \}=F(s)G(s)f*g=\int_{0}^{t} \ f(\tau )g(t-\tau ) d\tau

The Attempt at a Solution

Not quite sure how to approach this one with convolution and not solving the integral.

I need a t-τ instead of a t, but I can't have τ's in my Laplace because they won't go to S-space with any meaning.

Answer in book is :

\frac{3s^2+1}{s^2(s^2+1)^2}working backwards only leads me to a partial fraction type inverse transform.

Thanks in advance for help!

 

[vela]

Perhaps the idea is to use the property
$$\mathfrak{L}\{t f(t)\} = -F'(s) $$ where
$$f(t) = \int_0^t \sin \tau \, d\tau, $$ and to find F(s) using the convolution theorem.

 

[NJJ289]

Thanks Vela, that's exactly it