რადიუსი, დიამეტრი და წრეწირის სიგრძე

$d = 2r$d, equals, 2, r

$\dfrac{C}{d} = \redD{3{,}14159...}$start fraction, C, divided by, d, end fraction, equals, start color #e84d39, 3, comma, 14159, point, point, point, end color #e84d39

$\dfrac{C}{d} = \redD{\pi}$start fraction, C, divided by, d, end fraction, equals, start color #e84d39, pi, end color #e84d39

$C = \redD\pi d$C, equals, start color #e84d39, pi, end color #e84d39, d

$C = \pi d$C, equals, pi, d

$C = \pi \cdot 10$C, equals, pi, dot, 10

$C = 10\pi$C, equals, 10, pi