The expression:
[tex]\frac{2tan_{(x)} }{1+tan^2_{(x)}}[/tex]
is equivalent to which of the following and why? (please include appropriate equations if applicable)

a. tan(2 )x
b. sin(2 )x
c. 1 cos(2 ) ? x
d. cot(2 )x
e. none of the above