.
#(tantheta+sectheta-1)/(tantheta-sectheta+1)=(1+sintheta)/costheta#
#(sintheta/costheta+1/costheta-1)/(sintheta/costheta-1/costheta+1)=((sintheta+1-costheta)/costheta)/((sintheta-1+costheta)/costheta)=((sintheta+1)-costheta)/(sintheta+costheta-1)=#
#([(sintheta+1)-costheta][(sintheta+1)+costheta])/([(sintheta+costheta)-1][(sintheta+costheta)+1])=#
#([(sintheta+1)^2-cos^2theta])/([(sintheta+costheta)^2-1])=#
#(sin^2theta+2sintheta+1-cos^2theta)/(sin^2theta+2sinthetacostheta+cos^2theta-1)=(sin^2theta+2sintheta+sin^2theta)/(1+2sinthetacostheta-1)=#
#(2sintheta+2sin^2theta)/(2sinthetacostheta)=(2sintheta(1+sintheta))/(2sinthetacostheta)=(cancelcolor(red)(2sintheta)(1+sintheta))/(cancelcolor(red)(2sintheta)costheta)=#
#(1+sintheta)/costheta#