求sin18度-根号3cos18度/sin42度的值

问题描述:

求sin18度-根号3cos18度/sin42度的值

sin18度-根号3cos18度/sin42
=1/2(cos60°sin18°-sin60°cos18°)/sin42°
=1/2sin(18°-60°)/sin42d°
=-1/2