问一道很简单的三角函数题

│BA││BC│cos B=√3,S=1/2│BA││BC│sin B,1/2≤S≤3/2,
│BA││BC│=√3 / cos B,1/2≤1/2│BA││BC│sin B≤3/2,
1≤│BA││BC│sin B≤3,1≤√3sin B / cos B≤3,
1≤√3tan B ≤3,1/√3≤tan B ≤√3,√3/3≤tan B ≤√3,
又B是三角形ABC的内角,所以0度