已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a急

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已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a急
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已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a急
已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a

已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a急
答案如下

2sinacosa=(sina+cosa)^2-1=1,sinacosa=1/2;sina^2+cosa^2=1,联立一下sina+cosa=根号2,sina=cosa=根号2/2,tana=1,sin^4a+cos^4a=(sina^2+cosa^2)^2-2sin^2acos^2a,sinacosa=1/2,sin^4a+cos^4a=1/2