Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
Use the even-odd properties to find the exact value of the expression. Do not use a calculator.
- $\cos \left( - 60 ^ { \circ } \right)$

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