# Circles

## 18 terms · vocab. ch 10

### arc

a part of a circle that is defined by two endpoints

### center

the central point where radii form a locus of points called a circle

### central angle

an angle that intersects a circle in two points and has its vertex at the center of the circle

### chord

a segment with endpoints that are on the circle

### circle

the locus of all points in a plane equidistant from a given point called the center of the circle

### circumference

the distance around a circle

### circumscribed

a circle is circumscribed about a polygon if the circle contains all the vertices of the polygon

### diameter

a chord that passes through the center of the circle

### inscribed

a polygon is inscribed in a circle if each of its vertices line on the circle

### intercepted

an angle intercepts an arc if and only if each of the following conditions are met.
1. endpoints of arc lie on the angle
2. all points of arc except endpoints are in interior of circle
3. each side of angle contains an endpoint of arc

### major arc

an arc with a measure greater than 180

### minor arc

an arc with a measure less than 180

### pi

an irrational number represented by the ratio of the circumference of a circle to the diameter of the circle

### point of tangency

for a line that intersects a circle in only one point, the point at which they intersect

any segment with endpoints that are the center of the circle and a point on the circle

### secant

any line that intersects a circle in exactly two points

### semicircle

an arc that measures 180

### tangent

a line in the plane of a circle that intersects the circle in exactly one point. The point of intersection is called the point of tangency