sinα=1/3 cos2α=
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sinα=1/3cos2α=sinα=1/3cos2α=sinα=1/3cos2α=sinα=1/3cos2α=1-2sin^2α=1-2/9==7/9=1-2(sina)^2=7/9
sinα=1/3 cos2α=
sinα=1/3 cos2α=
sinα=1/3 cos2α=
sinα=1/3
cos2α=1-2sin^2α=1-2/9==7/9
=1-2(sina)^2=7/9
sin²α*sin²β+cos²α*cos²β-1/2cos2αcos2β=（1-cos2α）/2*（1-cos2β）/2+（1+cos2α）/2*（1+cos2β）/2-1/2cos2α*cos2β=1/4（1+cos2α*cos2β-cos2α-cos2β）+1/4（1+cos2α*cos2β+cos2α+cos2β）-1/2cos2α*cos2β=1/4+1/
sinα=1/3 cos2α=
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