1+sin(α-2π)*sin(π+α)-2cos^2(-α) 化简

化简sin(α+β)+sin(α-β)+2sinαsin(3π/2-β)= 2sin(α+π/3）=sinα+______ 为什么sin(2π-α)=-sinα? sin(π-α)=-2sin(π/2+α),则sinαcosα等于 sin(π-α)=-2sin(π/2+α),求sinα·cosα 已知sin(3π-α)=-2sin(π/2+α)则sinαcosα 化简1－sin[α－2π]sin[π＋α]－2sin²[－α]. 化简sin^2(α-π/6)+sin^2(α+π/6)-sin^2α 求sin^2α+sin^2(π/3 +α)+sin^2(π/3 -α) 求值sin^2(α-π/6)+sin^2(α+π/6)-sin^2α sin(π/4+α)sin(π/4-α)=1/4 求2sin^2(a) -1+tana-1/tan sinα=-1/2,π 设α,β,γ∈(0,π/2)且(sinα)^2+(sinβ)^2+(sinγ)^2=1求函数y=(sinα)^3/sinβ+(sinβ)^3/sinγ+(sinγ)^3/sinα 的最小值. (1-cos-sin)(1-sin+cos)/sin^2α-sinα ①利用公式sin(π-θ)=sinθ和sin(∏+θ)=-sinθ证明：sin（-θ）=-sinθ②证明tanθsinθ∕tanθ-sinθ=1+cosθ∕sinθ③已知sinα-2cosα+1=0,α≠kπ+π∕2,k∈z求：tan（3π-α）和1∕sin2α-sinαcosα+1的值‍ sin(π+α)=1/2,求sin(2π-α)-cot(α-π)cosα 化简 1+sin(α-2π)*sin(π+α)-2cos^2(-α) 1+sin(α-2π)*sin(π+α)-2cos^2(-α) 化简