Evaluate the Trigonometric Function $\tan \left( - \frac { \pi } { 8 } \right)$

Multiple Choice

Evaluate the trigonometric function.Round your answer to four decimal places.
$\tan \left( - \frac { \pi } { 8 } \right)$

A) 0.5858
B) -0.4142
C) 0.0858
D) 2.5858
E) 1.5858