Page 60 - Digibook MATH TRIGONOMETRY
P. 60
∆CBD ≅ ∆ABC (sebangun)
CD BC
BD AB =
= BC AC
BC AC 1 + cos 2θ 2 cos θ
sin 2θ 2 sin θ ⇔ =
⟺ = 2 cos θ 2
2
2 cos θ) 2 ∴ cos 2θ = 2 cos θ − 1
∴ sin 2θ = 2 sin θ cos θ
