2sinA(cosC/2)^2+2sinC（cos(A/2)）^2=3sinBsinA(1+cosC)+sinC(1+cosA)=sinA+sinC+sin(A+C)=sinA+sinC+sinB=3sinB所以sinA+sinC=2sinB即2sin[(A+C)/2]cos[(A-C)/2]=4sin(B/2)cos(B/2)因sin[(A+C)/2]=sin[(180°-B)/2...