A discrete Blaschke Theorem for convex polygons in $2$-dimensional space forms

Let $M$ be a $2$-space form. Let $P$ be a convex polygon in $M$. For these polygons, we define (and justify) a curvature ${\kappa }_i$ at each vertex $A_i$ of the polygon and and prove the following Blaschke’s type theorem: If $P$ is a convex plygon in $M$ with curvature at its vertices ${\kappa }_i\ge {\kappa }_0>0$, then the circumradius $R$ of $P$ satisfies $t{a}_{\lambda }(R)\le \pi \mathrm{/}(2{\kappa }_0)$ and the equality holds if and only if the polygon is a $2$-covered segment.