Nusukipenyo au rediasi ni mstari unaonyoka kati ya kitovu cha duara na mzingo wake. Ni nusu ya urefu wa kipenyo. Uhusiano kati ya mzingo na rediasi ni r = m 2 π {\displaystyle r={\frac {m}{2\pi }}} Definition and properties of the radius of a circle with interactive applet