$\mathrm {\int \dfrac{x d x}{\sqrt{1-x^{2}}}=f(x)+c}$ হলে $\mathrm {f(x)} =$ কত?

$\mathrm {\sin ^{-1} x}$

$\mathrm {\cos^{-1} x}$

$\mathrm {\ln \left(\sqrt{1-x^{2}}\right)}$

$\mathrm {-\sqrt{1-x^{2}}}$