(sinA-cosA+1)/(sinA+cosA-1)=(sinA-cosA+1)(sinA+cosA-1)/(sinA+cosA-1)^2;
(sin^2(A)-(cosA-1)^2)/(sin^2(A)+cos^2(A)-2cosA+2sinAcosA-2sinA+1)=
(sin^2(A)-cos^2(A)+2cosA-1)/(2-2cosA+2sinAcosA-2sinA)=
(cosA-cos^2(A))/(1-cosA+sinAcosA-sinA)=cosA(1-cosA)/(1-cosA-sinA(1-cosA))=
cosA(1-cosA)/((1-cosA)(1-sinA))=cosA/(1-sinA) QED