sin(40°-α)=1/3则 sin(10°+2α)的值等于 A.7/9 B.-7/9 C.-2/9 D.2/9

已知3sin²α+2sin²β=2sinα,求cos²α+cos²β的取值范围已知3sin²α+2sin²β=2sinα则有2sin²β=2sinα-3sin²α即sin²β=sinα-1.5sin²α所以cos²β=1-sin²β=1-(sinα-1.5sin²α)=1- sin²1°+sin²2°+sin²3°+……+sin²87°+sin²88°+sin²89°= sin²1°+sin²2°+sin²3°+...+sin²88°+sin²89°+sin²90°=等于多少? 已知3sinα=cosα,则sinα-2sinαcosα+3cosα+1= 若sin(α+β)=1/2,sinαcosβ=3/4,则sin(α-β)= 若sinβ=1/3,sin(α+β)=1,则sin(2α+β)=? 已知sinα+sinβ=1/3,则sinα-cos²β的最大值是 sinα+sinβ=1／3则sinα－cos²β的最大值是 2sinα-3cosα/4sinα-9cosα=-1,则9sin^2α-3sinαcosα-5= 已知sina=3/2sin^2α+sin^2β,则函数y=sin^2α+sin^2β的值域为1 已知sin(α+β)*sin(α-β)=-1/3,求sin^2α-sin^2β的值 sin²1°+sin²2°+sin²3°+.+sin²89°= -1为什么? sin²1°+sin²2°+sin²3°……sin²89°=? sin²1°+sin²2°+sin²3°……sin²89°= 求sin²1°+sin²2°+sin²3°……sin²89°=? sin²1°+sin²2°+sin²3°.+sin²89°= sinα=-2cosα,求sin^2α-3sinαcosα+1 已知sin(3π-α)=-2sin(π/2+α)则sinαcosα