&nbsp;Section+9.1+swann

=Section 9.1=

Objectives:

 * Define a circle and its associated parts, and use them in constructions.
 * Define and use the degree measure of arcs.
 * Define and use the length measure of arcs.
 * Prove a theorem about chords and their intercepted arcs.

Definitions:
at a given distance from a point within it called the center. sphere to the circumference or surface: (the radius of a circle is half the diameter.) of the circle. endpoints of the diameter. (it is also known as the half circle) is in the center of the circle. of the central angle and the other points are inside the angle.
 * **Circle:** a circle is a closed plane curve consisting of all points
 * **Radius:** a straight line extending from the center of a circle or
 * **Chord:** a segment in which its endpoints line up on the circle.
 * **Diameter:** a diameter is a cord which it includes the center point
 * **Arc:** a part of the circle were it isn`t broken.
 * **Endpoints**: any points that had divided into two parts.
 * **Semicircle:** it is an arc which the endpoints are the
 * **Minor arc:** It is an arc that is shorter then the semicircle.
 * **Major arc:** It is the arc that is longer then the semicircle.
 * **Central angle:** it is an angle in the plane whose vertex
 * **Intercepted arc**: When the endpoints of an arc are on the sides

Arc Length:
L=M/360°{2(3.14)r} -or- L=M/360°(2r)

Degree measure of arcs:
The central angle is the measure of a minor arc. The degree measure of a major arc is 360 degrees minus the degree measure of it's minor arc. The degree measure of a semicircle is 180 degrees, half of 360.

Finding the length of an arc:
r is radius of the circle and M is the degree measure of an arc of the circle, the length,L, of the arc is given by the following: L= M/360 degrees(2Pi r)