Added by Ruth Tedla on May 18, 2001 at 08:41:19:
1) sin2x = 2sinx cosx
2) cosx = cos^2x -sin^2x
or = 2cos^2x-1
or = 1- 2sin^2x
You can use which ever you are comfortableto do, when you find cosx.You have three choice.
3) tan2x = (2tanx)/(1-tan^2x)