Limits Continuity And Differentiability

If $f: R \rightarrow R$ defined by

$$ f(x)= \begin{cases}\frac{\sin x-\sin \frac{X}{2}}{x}, & x<0 \\ \frac{\sqrt{x^2+x}-\sqrt{x}}{x^{3 / 2}}, & x>0\end{cases} $$

is continuous on $R$, then $f(0)=$