Find the Exact Value of the Expression, If It Is $\cos \left( \tan ^ { - 1 } ( - \sqrt { 3 } ) \right]$

Multiple Choice

Find the exact value of the expression, if it is defined. $\cos \left( \tan ^ { - 1 } ( - \sqrt { 3 } ) \right]$

A) $- 1 / 2$
B) $\sqrt { 3 } / 3$
C) $\sqrt { 3 }$
D) $\sqrt { 3 } / 2$
E) $1 / 2$