Find the Derivative of Y with Respect to the Appropriate $$y = \sinh ^ { - 1 } ( \cos x )$$

Multiple Choice

Find the derivative of y with respect to the appropriate variable.
- $$y = \sinh ^ { - 1 } ( \cos x )$$

A) $- \sin x$
B) $\frac { 1 } { \sqrt { 1 + \cos ^ { 2 } x } }$
C) $\frac { - \sin x } { \sqrt { 1 + x ^ { 2 } } }$
D) $\frac { - \sin x } { \sqrt { 1 + \cos ^ { 2 } x } }$