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解:π/4+x的范围是5π/3<π/4+x<2π 角度在第四象限
根据cos(π/4+x)=3/5
得出sin(π/4+x)=-4/5
sinx+cosx=√2sin(π/4+x)=-4√2/5
(sinx+cosx)^2=32/25 所以2sinxcosx=(sinx+cosx)^2-1=7/25
cosx-sinx=√2cos(π/4+x)=3√2/5
(sin2x+2sin^2x)/(1-tgx)
=( 2sinxcosx+2sin^2x)/(1-sinx/cosx)
=2sinx(cosx+sinx)/ (1-sinx/cosx)
=2sinxcosx(cosx+sinx)/(cosx-sinx)
=-28/75
根据cos(π/4+x)=3/5
得出sin(π/4+x)=-4/5
sinx+cosx=√2sin(π/4+x)=-4√2/5
(sinx+cosx)^2=32/25 所以2sinxcosx=(sinx+cosx)^2-1=7/25
cosx-sinx=√2cos(π/4+x)=3√2/5
(sin2x+2sin^2x)/(1-tgx)
=( 2sinxcosx+2sin^2x)/(1-sinx/cosx)
=2sinx(cosx+sinx)/ (1-sinx/cosx)
=2sinxcosx(cosx+sinx)/(cosx-sinx)
=-28/75
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