A conducting wire is bent in the form of an n sided regular polygon enclosed by a circle of radius R. The magnetic field produced at its centre by a current i flowing through the wire is

A

$$\frac{\mu_0 i}{2 R} \frac{\sin\frac{\pi}{n}}{\frac{\pi}{n}}$$

B

$$\frac{\mu_0 i}{2 R} \frac{\cos\frac{\pi}{n}}{\frac{\pi}{n}}$$

C

$$\frac{\mu_0 i}{2 R} \frac{\tan\frac{\pi}{n}}{\frac{\pi}{n}}$$

D

$$\frac{\mu_0 i}{2 R} \frac{\cot\frac{\pi}{n}}{\frac{\pi}{n}}$$