Equations · equation
Circle: Circumference and Area
Vectors & Geometry · c. 250 BCE
- Equation
- C = 2πr, A = πr²
- Field
- Vectors & Geometry
- Symbols
- r radius · C circumference · A area · π the ratio of any circle's circumference to its diameter, 3.14159…
- Year
- -250
Significance
Archimedes squeezed π between 3 10/71 and 3 1/7 by fitting 96-sided polygons inside and outside a circle, and showed the area equals that of a right triangle with the radius and circumference as its legs — the first rigorous calculation of a curved figure. On a lathe the cutting speed is π × diameter × rpm; every wheel, pulley and orbit begins here.
Referenced by
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skill
Open on the Equations shelf — the interactive card, the filters, and everything alongside it.