15sin84° / sin 42°*sin 48°=30sin42cos42/sin42*sin48=30cos42/sin48=
=30cos(90-48)/sin48=30sin48/sin48=30
15sin84° / sin 42°*sin 48°=30sin42cos42/sin42*sin48=30cos42/sin48=
=30cos(90-48)/sin48=30sin48/sin48=30