Circles

A circle is a shape on a plane in which all points are equally distant from the center.

Terms and Symbols Related to Circles

TermSymbolDefinition
AreaaaThe amount of space occupied by the surface of the circle
CircumferenceccThe perimeter of a circle
DiameterddThe distance of a straight line from one point on a circle to the opposite point on the circle and passes through the center
Piπ\piThe ratio of a circle's circumference to its diameter. Equal to about 22/722/7 or 3.143.14
RadiusrrThe distance from the center to a point on the edge of a circle

Formulas to Find Properties of Circles

Area of a Circle

a=πr2a = \pi r^2

a=π(d/2)2a = \pi (d/2)^2

Circumference of a Circle

c=2πrc = 2 \pi r

c=dπc = d \pi

Diameter of a Circle

d=2rd = 2r

d=c/πd = c/\pi

Radius of a Circle

r=d/2r = d / 2

r=c/2πr = c/2\pi

Deeper Knowledge on Circles (Geometry)

Radian

The angle which subtends an arc equal to the length of the radius of a circle

Broader Topics Related to Circles (Geometry)

Geometry

The mathematics of shapes

Circles (Geometry) Knowledge Graph