cos(a+β)=3/5,cos(a-β)=12/13,0扫码下载作业帮拍照答疑一拍即得
问题描述：
cos(a+β)=3/5,cos(a-β)=12/13,0
扫码下载作业帮
拍照答疑一拍即得
答
∵0∴0
sin(a+β)=√[1-cos^2(a+β)]=4/5.
cos2a=cos[(a+β)+(a-β)]=cos(a+β)*cos(a-β)-sin(a+β)*sin(a-β)=16/65.