Prove $\displaystyle f(x)=\begin{cases} 3 \sin \left( \frac{1}{x} \right) \ \ \ \ \ x \neq 0\\ 0 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x=0\end{cases}$ is discontinuous at 0 using the $\displaystyle \epsilon-\delta$ definition for continuity.

So I gather that I need to find $\displaystyle \epsilon$ according to the definition $\displaystyle \exists \epsilon>0 \ s.t \forall \delta>0 \ |x-c|< \delta \Rightarrow \left|f(x)-f(c) \right|\geq \epsilon$

Umm....I have no idea how to start this. =S