In geometry, the radius of a circle or sphere, written as , is the shortest connection between the center and the boundary. It is either the distance from the center to the perimeter (in the case of a circle), or the distance from the center to the surface (in the case of a sphere). It is half of the diameter. That is, when r is the radius and d is the diameter:
r = d ÷ 2
d = 2 x r = r + r
The relationship between the radius and the circumference of a circle is
The area of a circle of radius is
Related pages[change | change source]
References[change | change source]
- "List of Geometry and Trigonometry Symbols". Math Vault. 2020-04-17. Retrieved 2020-09-24.
- Weisstein, Eric W. "Radius". mathworld.wolfram.com. Retrieved 2020-09-24.
- "Radius, diameter, & circumference | Circles (article)". Khan Academy. Retrieved 2020-09-24.
Other websites[change | change source]
- Definition and properties of the radius of a circle with interactive applet