Find the Exact Value by Using a Half-Angle Identity $\tan \frac { 7 \pi } { 8 }$

Multiple Choice

Find the exact value by using a half-angle identity.
- $\tan \frac { 7 \pi } { 8 }$

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