The sum of inradius and circum radius of incircle and circum circle of regular polygon of side n is

Let r and R be the inradius and cirumradius of incircle and circumcircle of the given regular polygon of side n. then, we know that $\mathrm{r}+\mathrm{R}=\frac{\mathrm{a}}{2}\cot \frac{\mathrm{\pi }}{\mathrm{n}}+\frac{\mathrm{a}}{2}\mathrm{cosec} \frac{\mathrm{\pi }}{\mathrm{n}}=\frac{\mathrm{a}}{2}\cot \frac{\mathrm{\pi }}{2\mathrm{n}}$