Let $\alpha \in \mathrm{R}$ be such that the function $$ f(x)= \begin{cases}\frac{\cos ^{-1}\left(1-\{x\}^2\right) \sin ^{-1}(1-\{x\})}{\{x\}-\{x\}^3}, & x \neq 0 \\ \alpha, & x=0\end{cases} $$ is continuous at $\mathrm{x}=0$, where $\{\mathrm{x}\}=\mathrm{x}-[\mathrm{x}]$, [x] is the greatest integer less than or equal to x . Then :