cos x sin x=3,求cos x+sin x
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cos x sin x=3,求cos x+sin x
因为cosxsinx=3,所以2cosxsinx=6
又因为(cosx+sinx)²=cos²x+2cosxsinx+sin²x
且cos²x+sin²x=1
所以cos²x+2cosxsinx+sin²x=6+1
(cosx+sinx)²=7
cosx+sinx=根号7
又因为(cosx+sinx)²=cos²x+2cosxsinx+sin²x
且cos²x+sin²x=1
所以cos²x+2cosxsinx+sin²x=6+1
(cosx+sinx)²=7
cosx+sinx=根号7
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