sin(π+α)=1/2,求sin(2π-α)-cot(α-π)cosα

sin(π-α)=-2sin(π/2+α),求sinα·cosα sin(π/4+α)sin(π/4-α)=1/4 求2sin^2(a) -1+tana-1/tan 化简sin(α+β)+sin(α-β)+2sinαsin(3π/2-β)= sin(π+α)=1/2,求sin(2π-α)-cot(α-π)cosα 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‍ 求sin^2α+sin^2(π/3 +α)+sin^2(π/3 -α) 2sin π/6 =sin π/3,吗,求解释,还有-sin π/6=sin- π/6吗 sinα=-2cosα,求sin^2α-3sinαcosα+1 已知sinα=4/5,求下列三角函数值1）sin（-α）2）sin（π-α）3）sin（π+α）4）sin（2π-α） 已知sin(α+β)*sin(α-β)=-1/3,求sin^2α-sin^2β的值 sinα+sinβ=1/3 求sinα-(cosβ）^2最大值 已知sinαsinβ=1/2,求cosαsinβ的范围. 已知-π/6＜=β＜π/4,3sin^2α-2sin^2β=2sinα,求sin^2β-1/2sin^2α的最值. 已知β∈[-π/6,π/4）,且3（sinα）^2-2（sinβ）^2=2sinα,求（sinβ）^2-1/2sinα的最小值 已知sin(x+π/6)=1/3,求sin(5π/6-x)+sin^2(π/3-x) 已知sin(x+π/6)=1/4,求sin(5π/6-x)+sin^2(π/3-x) 已知-π/2＜x＜0,sin x+cos x=1/5求sin 2x+2 sin