Answer? =b? +c? -2bc*cosA
=b? +c? -BC
Then 2cosA= 1
cosA= 1/2
A=60
From sine theorem:
c/b=sinC/sinB= 1/2+√3
sinC = sinB( 1/2+√3)C = 180-(A+B)
sin(A+B)=sinB( 1/2+√3)
sin(60+B)=sinB( 1/2+√3)
√3/2 cosb+ 1/2 sinb = 1/2 sinb+√3 sinb
√3/2cosB=√3sinB
tanB= 1/2