» Ringi raadius, pindala, ümbermõõt ja diameeter

\begin{align} A &= \pi r^{2} = \frac {\pi d^{2}}{4}\\ \\ C &= 2\pi r = \pi d\\ \\ d &= 2r\\ \\ \pi &= 3.1415926535897...\\ \\ 2\pi &= 6.28318530718...\\ \end{align}