证明sina*sinb=[cos(a-b)-cos(a+b)]/2

分类: 作业答案 • 2021-12-18 17:05:28

问题描述：

答

cos(a-b)=cosacosb+sinasinb (1)
cos(a+b)=cosacosb-sinasinb (2)
(1)-(2)
cos(a-b)-cos(a+b)=2sinasinb
sinasinb=[cos(a-b)-cos(a+b)]/2