Hi:

I am asked to prove the following identities:

a) 2cot2θ≡cotθ-tanθ

b) tan3θ≡3tanθ-tan³θ/1-3tan²θ

I think I should tackle the most complicated side as it is easier to aim for the easier looking side. (hope that makes sense )

I should warn you that I'm not good at this so please excuse my fumbling

a) 2cot2θ≡cotθ-tanθ

I will attempt the RHS, cotθ-tanθ

cotθ-sinθ/cosθ

so I'm stuck! Told you