### 5.21.14 Transform tan(x) into sin(x)/cos(x) : tan2sincos

tan2sincos takes as argument an expression containing
trigonometric functions.

tan2sincos replaces tan(x) by
sin(x)/cos(x) in this expression.

Input :

tan2sincos(tan(2*x))

Output :

sin(2*x)/cos(2*x)