问题描述: 和差化积公式如何推导来的,只要举一个例子! 1个回答 分类:数学 2014-11-04 问题解答: 我来补答 sinx+siny=sin[(x+y)/2+(x-y)/2]+sin[(x+y)/2-(x-y)/2]=sin(x+y)/2 cos(x-y)/2 + sin(x-y)/2 cos(x+y)/2+sin(x+y)/2 cos(x-y)/2 - sin(x-y)/2 cos(x+y)/2=2sin(x+y)/2 cos(x-y)/2 展开全文阅读