三角函數 - Mind Map
3.tanθ=sinθ/cosθ. 4.tanθ=1/tan(90o-θ). 5.sinθ=2sin(θ/2)cos(θ/2) 6.cosθ=1-2sin2(θ/2) 7.sin(θ/2)=±√½(1-cosθ) 8.cos(θ/2)=±√½(1+cosθ) 9.tan(θ/2)=±√(1-cosθ)/(1+cosθ) =1-cosθ/sinθ =sinθ/(1+cosθ). 10.(sinx)(cosy)=½[sin(x+y)+sin(x-y)] 11.(cosx)(siny)=½ ......