The Laplace transform of a function $f(t)$ is $L( f )=\dfrac{1}{(s^{2}+\omega ^{2})}.$ Then, $f(t)$ is

1. $f\left ( t \right )=\dfrac{1}{\omega ^{2}}\left ( 1-\cos\:\omega t \right ) \\$
2. $f\left ( t \right )=\dfrac{1}{\omega}\cos\:\omega t \\$
3. $f\left ( t \right )=\dfrac{1}{\omega}\sin\:\omega t \\$
4. $f\left ( t \right )=\dfrac{1}{\omega^{2}}\left ( 1-\sin\:\omega t \right )$