question_answer

The derivative of \[\mathbf{se}{{\mathbf{c}}^{-\mathbf{1}}}\left( \frac{-1}{2{{x}^{2}}+1} \right)\]with respect to \[\sqrt{1-{{\mathbf{x}}^{\mathbf{2}}}}\]at \[\mathbf{x}=\frac{1}{2}\]is equal to:

A) (a) 4                             

B) (b) \[-4\]             

C) (c) 2                             

D) (d) \[-2\]