Use a Sum or Difference Identity to Find the Exact $\frac { \sin ^ { 2 } x - 1 } { \cos ( - x ) }$

Multiple Choice

Use a sum or difference identity to find the exact value.
- $\frac { \sin ^ { 2 } x - 1 } { \cos ( - x ) }$

A) $- \cos x$
B) $\sin x$
C) $\cos x$
D) $- \sin x$