Circle Geometry and Formulas

Front

Center

Back

The fixed point from which all points on the circle are equidistant.

Front

Radius (r)

Back

Distance from the center to any point on the circle.

Front

Diameter (d)

Back

A chord that passes through the center; d = 2r.

Front

Circumference (C)

Back

The perimeter or distance around the circle.

Front

Chord

Back

A line segment with both endpoints on the circle.

Front

Arc

Back

A part of the circumference.

Front

Sector

Back

A 'pizza slice' of the circle, bounded by two radii and the arc.

Front

Segment

Back

Area between a chord and the arc it subtends.

Front

Tangent

Back

A line that touches the circle at exactly one point.

Front

Secant

Back

A line that intersects the circle at two points.