cos(a+b)的展开证明

网址引用：https://blog.csdn.net/rgbhi/article/details/117628576

OA=1

cos(\alpha +\beta )=OB

OB=OD-BD

BD=EC

EC=AC*sin(\beta )=OA*sin(\alpha )*sin(\beta )

OD=OC*cos(\beta )=OA*cos(\alpha )*cos(\beta )

\therefore cos(\alpha +\beta )=cos(\alpha )*cos(\beta )-sin(\alpha)*sin(\beta )

posted @ 2022-07-14 22:32  MaxBruce  阅读(995)  评论(0)    收藏  举报