Question

prove that:

cos (2 x 30°) = `(1 – tan^2 30°)/(1+tan^2 30°)`

Answer 1

RHS,

`(1 – tan^2 30°)/(1 +tan^2 30°) = (1–(1)/(3))/(1+(1)/(3)) = (1)/(2)`

LHS,

cos (2 x 30°) = `cos 60° = (1)/(2)`

LHS = RHS