Find the Exact Value of the Trigonometric Function $\cos \left( \frac { \pi } { 4 } \right)$

Multiple Choice

Find the exact value of the trigonometric function. Do not use a calculator or tables.
- $\cos \left( \frac { \pi } { 4 } \right)$

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