Use a Reference Triangle in an Appropriate Quadrant to Find $\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)$

Multiple Choice

Use a reference triangle in an appropriate quadrant to find the angle.
- $\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)$

A) $\frac { 4 } { \pi }$
B) $\frac { \pi } { 2 }$
C) $\frac { 2 \pi } { 3 }$
D) $\frac { 3 \pi } { 4 }$