Question

If m tan(θ − 30°) = n tan(θ + 120°) show that the value of cos2θ in terms of m and n is (m + n)/2(m + n).

Answer 1

Given m tan(θ − 30°)  = n tan(θ  - 120°) = n tan(90° + 30° + θ)  = -ncot(30° + θ)