What Are the Values of a for Which the Given Function is Continuous at x=0?

[Yankel]

Hello

I need some help with this question please:

For which values of a the next function is continuous at x=0 ?

\left\{\begin{matrix} x^{a}\cdot sin\frac{1}{x} & x\neq 0\\ 0 & x=0 \end{matrix}\right.

I know that for it to be continuous at x=0, I need f(0)=lim x-->0

So I tried calculating the limit, and got to:

\lim_{x\to0}x^{a-1}\cdot sin\frac{1}{x}\cdot xnot sure I am correct, but anyhow do not know how to proceed. What I tried to do was to bring the limit to a known form

 

[Ackbach]

I would think about the squeeze theorem, and the fact that $-1\le \sin(x)\le 1\;\forall\,x$.