已知sinx+cosx=1/5
sin^2x+2sinxcosx+cos^2x=1/25
2sinxcosx=-24/25
sin^2x-2sinxcosx+cos^2x=1/25-4sinxcosx
(sinx-cosx)^2=1/25-2*(-24/25)
(cosx-sinx)^2=49/25
x在第四象限,cosx>sinx
cosx-sinx=7/5
2sinx*cosx+2sin²x/1-tanx
=[2sinx(cosx+sinx)]/[(1-sinx/cosx)]
=[2sinxcosx(cosx+sinx)]/(cosx-sinx)
=[-24/25*1/5]/(7/5)
=-24/175