2sin^2σ*sin^2β+2cos^2σcos^2β=1+cos2σ*cos2β

sin(α+β)-2sinαcosβ/2sinαsinβ+cos(α+β) 2sin@+cos@等于? 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos 化简sin^2α+sin^2β+2sinαsinβcos(α+β) 求证:sin(2α+β)/sinα-2cos(α+β)=sinβ/sinα 求证sin(2α+β)/sinα-2cos(α+β)=sinβ/sinα 求证sin(2α+β)/sinα-2cos(α+β)=sinβ/sinα 求证sin(2α+β)/sinα-2cos(α+β)=sinβ/sinα 证明：sin(2α+β)/sinα - 2cos(α+β)=sinβ/sinα sin(α+β)-2cosαsinβ/2cosαcosβ-cos(α+β) 证明cosα(cosα-cosβ)+sinα(sinα-sinβ)=2sin^2(α-β/2)第二个 证明sin(α+β)cosα-1/2[sin(2α+β)-sinβ]=sinβ 化简sin(α+β)-2sinαsinβ/2sinαsinβ+cos(α+β) 求证：sin²α+sin²β+2sinαsinβcos(α+β)=sin²(α+β) 化简sin^2α+sin^2β-sin^2αsin^2β+cos^2cos^2β 化简sin^2α+sin^2β-sin^2cos^2β-cos^2αsin^2β 求证sin^2α+sin^2β-sin^2αsin^2β+cos^2cos^2β=1 求值:sin^2α+sin^2β-sin^2α×sin^2β+cos^2α×cos^2β 化简sin^2a+sin^β-sin^2a*sin^2β+cos^2a*cos^β