最佳回答取２０分：兩條Trigonometric Relations問題

1.Find the measure of θ if cos(30∘+4θ) = cos(2θ+30∘)/tan(60∘-2θ)

Ans:5°

2. Prove the following isentities.

(a) sin(90∘-θ)sinθ/sinθ-1 + cos(90∘-θ)cosθ/sinθ+1 ≡ -2sinθ/tan(90∘-θ)

(b) [cosθtanθ+cos(90∘-θ)tan(90∘-θ)]² - 2sinθsin(90∘-θ) ≡1

對不起,本人不太會prove identities=]

希望幫到你啦

自問自答

1.tan x=3
sin x/cos x=3
cos x=1/3‧sin x

sin^2 x + cos^2 x = 1
1/9‧sin^2 x+sin^2 x=1
sin^2 x=9/10
sin x=3/√10