化简sin^4x-sin^2+cos^2化简(1)sin^4x-sin^2+cos^2(2)根号(1+cosα/1-cosα)+根号(1-cosα/1+cosα)(180°<α<270°)

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化简sin^4x-sin^2+cos^2化简(1)sin^4x-sin^2+cos^2(2)根号(1+cosα/1-cosα)+根号(1-cosα/1+cosα)(180°<α<270°)
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化简sin^4x-sin^2+cos^2化简(1)sin^4x-sin^2+cos^2(2)根号(1+cosα/1-cosα)+根号(1-cosα/1+cosα)(180°<α<270°)
化简sin^4x-sin^2+cos^2
化简(1)sin^4x-sin^2+cos^2
(2)根号(1+cosα/1-cosα)+根号(1-cosα/1+cosα)(180°<α<270°)

化简sin^4x-sin^2+cos^2化简(1)sin^4x-sin^2+cos^2(2)根号(1+cosα/1-cosα)+根号(1-cosα/1+cosα)(180°<α<270°)
(1) (sinx)^4 - (sinx)^2 + (cosx)^2
=(1-cos2x)^2/4 + cos2x
= [ 1 - 2 cos2x + (cos2x)^2 + 4 cos2x ] / 4
= ( 1 + cos2x )^2 /4
= [ ( 1 + cos2x ) / 2 ]^2
= (cosx)^4

(1)sin^2x(sin^2x-1)+cos^2x-->sin^2x(-cos^2x)+cos^2x-->cos^2x(1-sin^2x)-->cos^4x
(2) 表达式大于0,所以将表达式平方,表达式^2=(1+cosα)/(1-cosα)+(1-cosα)/(1+cosα)+2=
4/sin^2α,所以表达式=-2/sinα(因为表达式为正,所以前面加-号)