FRAC{\
COS
\frac{B-
C
}{
2
}}{\
SIN
\frac{A}{2}}=\frac{\sin \frac{B+C}{2}\cos \frac{B-C}{2}}{\sin \frac{B+C}{2}\sin \frac{A}{2}}=\frac{\sin B+\sin C}{\sin A}=\frac{b+c}{a}\].