Question

tan^2 u = (1-cos2u)/(1+cos2u)
explain why this identity does not imply that tan u = square root of (1-cos2u)/(1+cos2u)

Answer 1

i think the first step will be writing tan^2 u using sin u and cos u
- hope so much that you know it

Answer 2

I don't really see why it wouldn't... the converse wouldn't be true though.