5 sin72 / sin36 * cos 54

Question

5 sin72 / sin36 * cos 54

Answer 1

5sin72°/(sin36° *cos54°)=5sin(2*36°)/(sin36° *cos54°)=
=5*(2sin36° *cos36°)/(sin36° *cos54°)=
=10cos36°/cos54°=10cos36°/cos(180°-36°)=10cos36°/(-cos36°)=-10