ABC成等差数列得B=60,由正弦定理得,sinAsinC/（sinB）^2=ac/b^2,得sinAsinC=1/2,有余弦定理得a+c=√3b,a+c/sinA+sinC=b/sinB,得3/2,得sinA=1/2或1,故a=30或90.