Circle Basics Advanced Geometry

CIRCLE A circle is the locus or set of all points in a plane that are equidistant from a given point, called the center.

RADIUS The distance from the center to a point on the circle is the radius of the circle. All radii of a circle are congruent.

CONGRUENT CIRCLES Two circles are congruent if they have the same radius.

CHORD A chord is a segment whose endpoints are points on the circle.

DIAMETER The distance across the circle, through its center, is the diameter of the circle. A chord that passes through the center and is made up of collinear radii.

The diameter is twice the radius.

SECANT A secant is a line that intersects a circle in two points.

SECANT The diameter is a chord, but it is part of a secant. If the diameter was extended on both sides, then it would be called a secant.

TANGENT A tangent is a line in the plane of a circle that intersects the circle in exactly one point.

POINT OF TANGENCY The point at which a tangent line intersects the circle to which it is tangent is the point of tangency.

IDENTIFY THE PARTS OF THE CIRCLE K C B J D E H F G

INTERIOR AND EXTERIOR OF A CIRCLE The interior of a circle consists of the points that are inside the circle. The exterior of a circle consists of the points that are outside the circle.

Example Circles B and E have radii of 8 cm & 6 cm respectively, and CD is 3 cm. Use this information to determine the missing values. BC EA Perimeter of BGEH AF Perimeter of ∆BGE