Find the Expression as the Tangent of an Angle $\frac { \tan 60 ^ { \circ } - \tan 20 ^ { \circ } } { 1 + \tan 60 ^ { \circ } \tan 20 ^ { \circ } }$

Multiple Choice

Find the expression as the tangent of an angle.
$\frac { \tan 60 ^ { \circ } - \tan 20 ^ { \circ } } { 1 + \tan 60 ^ { \circ } \tan 20 ^ { \circ } }$

A) $\tan 40 ^ { \circ }$
B) $\tan 60 ^ { \circ }$
C) $\tan ^ { - 1 } 80 ^ { \circ }$
D) $\tan 20 ^ { \circ }$
E) $\tan ^ { - 1 } 40 ^ { \circ }$