If A, B, C are the angles of a $$\triangle\ ABC$$ then the following is equal to; $$\sin \left(\frac{B+C}{2}\right)$$

A

$$\sec \frac{B}{2}$$

B

$$\sec \frac{A}{2}$$

C

$$\cos \frac{A}{2}$$

D

$$\cosec \frac{A}{2}$$