Circles

Front

Radius

Back

The distance from the center of a circle to any point on its circumference.

The radius is 1/2 the length of the diameter.

Front

Diameter

Back

A line segment that passes through the center of the circle and has its endpoints on the circle. It is also the longest distance across the circle.

This is made of 2 radii.

Front

Circumference

Back

The total distance around the circle.

Front

Chord

Back

A line segment with both endpoints on the circle.

Front

Arc

Back

A part of the circumference of a circle.

Front

Arc Length

Back

The distance along the curved line making up the arc.

Front

Sector Area

Back

The area of a sector, which is a 'slice' of the circle.

Front

Tangent Line (to a circle)

Back

A line that touches the circle at exactly one point.

Front

Circumscribed Circle

Back

A circle that passes through all the vertices of a polygon.

Front

Inscribed Circle

Back

A circle that is contained within a polygon and touches all its sides.