Use the Appropriate Addition Formula to Find the Exact Value $\cos \left( - \frac { 7 \pi } { 12 } \right)$

Multiple Choice

Use the appropriate addition formula to find the exact value of the expression.
- $\cos \left( - \frac { 7 \pi } { 12 } \right)$

A) $\frac { \sqrt { 6 } - \sqrt { 2 } } { 4 }$
B) $\frac { \sqrt { 2 } - \sqrt { 6 } } { 4 }$
C) $\sqrt { 2 } - \sqrt { 6 }$
D) $\sqrt { 6 } + \sqrt { 2 }$