Sin18 cos36 - sin36 sin72/sin72 cos54 - sin54 sin18

Question

Sin18 cos36 - sin36 sin72/sin72 cos54 - sin54 sin18

Answer 1

(sin18cos36-sin36sin(90-18))/(sin(90-18)cos54-sin54sin18)=
=(sin18cos36-sin36cos18)/(cos18cos54-sin54sin18)=sin(18-36)/cos(54+18)=
=-sin18/cos(90-18)=-sin18/sin18=-1