Question

Prove:

Cot x cot 2x - cot 2x cot 3x - cot 3x cot x = 1

Answer 1

google is your friend. See

https://www.teachoo.com/2194/584/Ex-3.3--22---Prove-cot-x-cot-2x---cot-2x-cot-3x---cot-3x-cot-x/category/Ex-3.3/