sin^4x+cos^4x=5/9 求sin2X
2个回答
sin^4x+cos^4x=5/9
(sin^2x+cos^2x)^2-2sin^2xcos^2x=5/9
1-sin^2(2x)/2=5/9
sin^2(2x)=8/9
sin2X=正负2根号2/3
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