Reidius

Is e reidius an t-ainm airson an astar eadar cearcall agus a lar. Is feart do cearcall sam bith gu bheil luach cunbhalach air an reidius aige.

Is lar ainm airson puing meadhanach.

Seo reidius dhen chearcall leis a' chearcall-thomhas C:

${\displaystyle r={\frac {C}{2\pi }}.}$