学帮网如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA
来源：学生作业学帮网 编辑：学帮网 时间：2024/05/30 12:11:58
如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA
sin(2a+b)/sina-2cos(a+b)=sinb/sina ==>左边=[sin(2a+b)-2cos(a+b)sina]/sina =[sina*cos(a+b)+sin(a+b)*cosa-2cos(a+b)sina]/sina =[sin(a+b)*cosa-cos(a+b)sina]/sina =sin(a+b-a)/sina=sinb/sina=右边