题目

题型：解答题难度：一般来源：不详

化简

(sinx+cosx-1)(sinx-cosx+1)

sin2x

．

答案

原式=

(sinx+1-2sin2 x 2 -1)(sinx-1+2sin2 x 2 +1)

sin2x

=

(2sin x 2 cos x 2 -2sin2 x 2 )(2sin x 2 cos x 2 +2sin2 x 2 )

4sin x 2 cos x 2 cosx

=

(cos x 2 -sin x 2 )(cos x 2 +sin x 2 )•sin x 2

cos x 2 cosx

=

(cos2 x 2 -sin2 x 2 )sin x 2

cos x 2 •cosx

=

cosx•sin x 2

cos x 2 •cosx

=tan

x

2

．