Circle modeling the earth. O is the center of the earth, r the radius of the earth, and h the height…

Illustration of a circle that can be used to show that an "angle at the center of a circle is measured…

Illustration of a circle that can be used to show that an "angle at the center of a circle is measured…

Illustration of a circle that can be used to show that an "angle at the center of a circle is measured…

Illustration of a circle showing an angle included by a tangent and a chord drawn from the point of…

Circle with chord AB=2 ft. and radius OA = 3 ft.. Triangle AOC is a right triangle. Angle AOC=half angle…

Illustration of a circle with diameter AB. Radii are RO, SO, AO, and BO. ED is a chord.

Illustration of a circle with diameter BC, chord DF, secant MN, and tangent HK.

Illustration of a circle which illustrates that through three points not in a straight line one circumference,…

Illustrations of a circle with a circumscribed polygon. Or, a circle inscribed in an octagon.

Illustration showing the definition of a circle as a conic section. The section of a right circular…

An illustration showing the intersection of a plane and a cone. The cone is intersected by a plane parallel…

Illustration of a decagon circumscribed about a circle. This can also be described as a circle inscribed…

Illustration of a decagon inscribed in a circle. This can also be described as a circle circumscribed…

Illustration of a circle with diameter and chord drawn. A diameter perpendicular to a chord bisects…

Illustration used to show that "The diameter perpendicular to a chord bisects the chord and also its…

Illustration showing a circle with a diameter, radius, and segment drawn.

Illustration showing a circle with a diameter, radius, lines, triangle, and segment drawn.

Illustration of a dodecagon circumscribed about a circle. This can also be described as a circle inscribed…

Illustration of a dodecagon inscribed in a circle. This can also be described as a circle circumscribed…

Illustration of a circle with equal chords, which are equally distant from the center.

An illustration showing how to find the center of a circle which will pass through three given points…

Illustration of a hexagon in a circle. Four of the six vertices of the hexagon are bound by the circle…

Illustration of hexagon inscribed in circle. Or, circle circumscribed about hexagon.

Illustration of a circle with an angle inscribed in a segment greater than a semicircle, an acute angle.

Illustration of a circle with an angle inscribed in a segment less than a semicircle, an obtuse angle.

Illustration showing the diameter of a circle inscribed in a right triangle is equal to the difference…

Illustration of a circle with a right angle inscribed in a semicircle.

Illustration showing a circle with equilateral triangles and another circle within.

"A circle may be conceived as a polygon of an infinite number of sides. Thus to draw the involute of…

Illustration of a regular nonagon inscribed in a circle. This could also be described as a circle circumscribed…

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon.

"If from any point on the circumference of a circle, a perpendicular be let fall upon a given diameter,…

Illustration of polygon circumscribed about circle. Or, circle inscribed in the polygon.

Illustration of polygon inscribed in circle. Or, circle circumscribed about the polygon.

Illustration of a quadrilateral circumscribed about a circle. This could also be described as a circle…

An illustration showing a quadrilateral inscribed in a circle that is tangent to a line.

Illustration of circle with radius of 4000, and triangle with 45 degree angle enclosed.

An illustration showing a circle with radius r, diameter d, and chord c.

Illustration of a regular heptagon/septagon inscribed in a circle. This can also be described as a circle…

Illustration of a regular hexagon circumscribed about a circle. This can also be described as a circle…