Prove 1+sintita-costita whole square/1+sintita +xostita whole square=1-costita/ 1+costita

(1+sintheta-costheta)²/(1+sintheta+costheta)=[1+sin²theta+2sintheta+cos²theta-2costheta(1+sintheta)]/[1+sin²theta+cos²theta+2sintheta+2costheta(1+sintheta)]=[2(1+sintheta)-2costheta(1+sintheta)]/[2(1+sintheta)+2costheta(1+sintheta)]=[2(1+sintheta)(1-costheta)]/[2(1+sintheta)(1+costheta)]= (1-costheta)/(1+costheta)