正弦定理：a/sinA=c/sinC
AB/BC=sinC/sinA
sinC=1/2
∵C为钝角
∴∠C=150°
则cosC=-√3/2
cosA=±√[1-(sinA)^2]=±2√2/3
∵在三角形ABC中,C为钝角
∴cosA=2√2/3
sinB=sin[π-(A+C)]=sin(A+C)=sinAcosC+sinCcosA=(2√2-√3)/6