I have to solve simple task using Ito's formula. The goal is to find $$ E[\sin(\sigma W_t)] $$ where $W_t$ is Wiener process.
I know that we have to use function $$ F(t,x)=\sin(\sigma x) $$ and then Ito's formula.
I know that $$ dx(t)=a(t)dt+b(t)dW(t) $$ However I do not see why im my exercise I should take functions $a(t)=0, b(t)=1$ because we do have neither $dt$ nor $dW(t)$. To sum up I want to ask how to find those functions in that kind of exercises.