4sinAsinC-2cos(A-C)=1
4sinAsinC-2(cosAcosC+sinAsinC)=1
2sinAsinC-2cosAcosC=1
cos(A+C)=-1/2 ∵ A+C= π-B
∴cos(π-B)=-1/2
cosB=1/2 B=π/3
4sinAsinC-2cos(A-C)=1
4sinAsinC-2(cosAcosC+sinAsinC)=1
2sinAsinC-2cosAcosC=1
cos(A+C)=-1/2 ∵ A+C= π-B
∴cos(π-B)=-1/2
cosB=1/2 B=π/3