Prove the trigonometric identities. 2 cosθ sinθ / tan(90°- θ) ≡ 2sin²θ?

2 cosθ sinθ / tan(90°- θ)
=2 cosθ sinθ / (1 / tanθ)
=2 cosθ sinθ tanθ
=2 cosθ sinθ × sinθ/cosθ
=2sin²θ

Prove the trigonometric identities. 2CosθSinθ/Tan(90°-θ)≡2Sin^2 θ?編輯
Sol
2CosθSinθ /Tan(90°-θ)
=2CosθSinθ /Cotθ
=2CosθSinθ /(Cosθ/Sinθ)
=2Sin^2 θ