acosC+√3asinB-b-c=0
利用正弦定理 a/sinA=b/sinB=c/sinC
sinAcosC+√3sinAsinC-sinB-sinC=0
∵ sinB=sin(A+C),
sinAcosC+√3sinAsinC-sin(A+C)-sinC=0
sinAcosC+√3sinAsinC-sinAcosC-cosAsinC-sinC=0
√3sinAsinC=sinC+cosAsinC
√3sinA=1+cosA
2√3sin(A/2)cos(A/2)=2cos²(A/2)
√3tan(A/2)=1
tan(A/2)=√3/3
∵0