1、y=2cosx(sinx+cosx)/[(sinx-cosx)(sinx+cosx)]
=(2sinxcosx+2cos²x)/(sin²x-cos²x)
=(sin2x+1+cos2x)/(-cos2x)
=-(1+sin2x)/cos2x-1
=-(sinx+cosx)²/[(cosx+sinx)(cosx-sinx)]-1
=(sinx+cosx)/(sinx-cosx)-1
=(tanx+1)/(tanx-1)-1
tanx≠1
x≠kπ+π/4且x≠kπ+π/2 ,k∈Z
{x｜x∈R且x≠kπ+π/4且x≠kπ+π/2,k∈Z}
2、f(x)=(1+sinx-cosx)/(1+cosx+sinx)
=[2sin²(x/2)+2sin(x/2)cos(x/2)]/[2cos²(x/2)+2sin(x/2)cos(x/2)]
=sin(x/2)[sin(x/2)+cos(x/2)]/{cos(x/2)[sin(x/2)+cos(x/2)]}
=sin(x/2)/cos(x/2)
=tan(x/2)
x/2≠kπ+π/2
x≠2kπ+π
定义域：{x｜x∈R且x≠2kπ+π,k∈Z}