$\int \frac{d x}{\sqrt{2-x^{2}}}=?$

$\sin ^{-1} \frac{x}{\sqrt{2}}+C$

$\sin ^{-1} \frac{x}{2}+C$

$\sin ^{-1} \frac{x}{\sqrt{2}}$

$\sin ^{-1} \frac{x}{2}$