(sin75度-sin15度)*(cos15度+cos75du)的值
问题描述:
(sin75度-sin15度)*(cos15度+cos75du)的值
答
令x=75度,y=15度,=sinxcosy+sinxcosx-sinycosy-sinycosx
=sin(x-y)+cos(x+y)=sin60+cos90=根号3/2