Question

if A = 30 degrees

verify that

cos 2A = (1-tan2 a) / (1+ tan2 a)

Answer 1

take lhs
cos 2 30=cos 60 = 1/2
take rhs
(1-tan 2*30)/(1+tan 2*30)
= 1-tan6o/1+tan6o
=1-√3/1+√3 =1/2 hence proved