en.wikipedia.org/wiki/Circle

A circle is a simple closed shape in Euclidean geometry. It is the set of all points
in a plane that are at a given distance from a given point, the centre; equivalently
...

www.khanacademy.org/math/geometry-home/cc-geometry-circles

Explore, prove, and apply important properties of circles that have to do with
things like arc length, radians, inscribed angles, and tangents.

www.coolmath.com/reference/circles-geometry

Definitions and formulas for the radius of a circle, the diameter of a circle, the
circumference (perimeter) of a circle, the area of a circle, the chord of a circle, arc
...

www.mathwarehouse.com/geometry/circle/

Circle worksheets, videos, tutorials and formulas involving arcs, chords, area,
angles, ... Circles Worksheets and Activities for Math Teachers ... back to
Geometry ...

www.mathgoodies.com/lessons/vol2/geometry.html

A circle is an important shape in the field of geometry. Let's look at the definition
of a circle and its parts. We will also examine the relationship between the circle ...

www.mathplanet.com/education/geometry/circles/basic-information-about-circles

A circle is all points in the same plane that lie at an equal distance from a center
point. The circle is only composed of the points on the border. You could think of
...

www.mathsisfun.com/geometry/circle.html

Geometry Index ... circle. A circle is easy to make: Draw a curve that is "radius"
away from a ... radius diameter circumference: circle/diameter = pi = 3.14159.

www.mathsisfun.com/geometry/circle-theorems.html

Some interesting things about angles and circles. ... Inscribed Angle: an angle
made from points sitting on the circle's circumference. inscribed ... Geometry
Index.

www.regentsprep.org/regents/math/geometry/gp15/circleangles.htm

www.math.com/tables/geometry/circles.htm

Circles. (Math | Geometry | Circles) ... arc: a curved line that is part of the
circumference of a circle ... Circumference of Circle = PI x diameter = 2 PI x radius