sin(α+2/5π)化简成sin(2/π+α)为什么

化简sin(α+β)+sin(α-β)+2sinαsin(3π/2-β)= 计算,sin(π/12)-sin(5π/12)+2sin(π/8)sin(3π/8) sin(α+2/5π)化简成sin(2/π+α)为什么 2sin(α+π/3）=sinα+______ 为什么sin(2π-α)=-sinα? sin(5π+π/2+α) sinα=4/5,π/2 若（sinα+cosα）/（sinα-cosα）=2 则sin(α-5π)·sin(3π/2-α)=? 若sinα+cosα/sinα-cosα=2,则sin(α-5π）*sin（3π/2-α）等于? 若(sinα+cosα)/(sinα-cosα)=2,求sin(α-5π)sin(3π/2-α)的值 sin(3/2-5α) 已知sin（2α+ β）=5sinβ,求证：2sin（α+ β）=3sinα 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