Question

If θ = 30°, prove that cos 2θ = cos22θ – sin22θ

Answer 1

$\huge\mathfrak{Solution}$

if θ = 30°

➡ cos 2θ = cos 22θ - sin22θ

➡cos 2 × 30° = 1 [ cosθ - sinθ = 1]

➡ cos 60°

➡$\cos(60) \: = \frac{1}{2}$