如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA
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![如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA](/uploads/image/z/2739120-24-0.jpg?t=%E5%A6%82%E9%A2%98+%E6%B1%82%E8%AF%81sin%282A%2BB%29%2FsinA%2B2cos%28A%2BB%29%3DsinB%2FsinA)
如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA
如题 求证sin(2A+B)/sinA+2cos(A+B)=sinB/sinA
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