Use an Identity to Write the Expression as a Single $\sin 22.5 ^ { \circ }$

Multiple Choice

Use an identity to write the expression as a single trigonometric function or as a single number.
- $\sin 22.5 ^ { \circ }$

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