(1)(cosx+sinx)/(cosx-sinx)=(1+tanx)/(1-tanx)=(1+2)/(1-2)=-3
(2)sinxcosx-1=sinxcosx/[(sinx)^2+(cosx)^2]-1=tanx/[1+(tanx)^2]-1=2/5-1=-3/5
(3)2+sinxcosx-(cosx)^2=2+[sinxcosx-(cosx)^2]/[(sinx)^2+(cosx)^2]
=2+[tanx-1]/[(tanx)^2+1]=2+(2-1)/(4+1)=2+1/5=11/5