cosπ/4cosx-sinπ/4sinx=3/5
cosx-sinx=3√2/5
平方
cos²衫凯x+sin²x-2sinxcosx=18/25
1-2sinxcosx=18/25
sinxcosx=7/50
sinx+cosx=√2sin(x+π/4)
5π/4
所以sinx+cosx<0
(sinx+cosx)²=sin²x+cos²x+2sinxcosx=1+7/25=32/25
sinx+cosx=-4√2/5
原式或滑唤=(2sinxcosx+2sin²x)/让游(1-sinx/cosx)
=2sinx(cosx+sinx)/[(cosx-sinx)/cosx]
=2sinxcosx(cosx+sinx)/(cosx-sinx)
=-28/75