sinθ/(1+cosθ)
=2sin(θ/2)cos(θ/2)/2cos²(θ/2)
=sin(θ/2)/cos(θ/2)
=tan(θ/2)
提示:分子分母分别用倍角公式,然后约分。
sinθ/(1+cosθ)={2sin(θ/2)cos(θ/2)}/2{cos(θ/2)}^2=sin(θ/2)/cos(θ/2)=tan(θ/2)
因为sinθ=2sinθ/2cosθ/2 cosθ=2cos(θ/2)^2-1
sinθ/(1+cosθ)=2sinθ/2*cosθ/2/cos^2(θ/2 )=sinθ/2/cosθ/2=tan(θ/2)
sin0=2sin0/2cos0/2 1+cos0=2cos^20/2