## 30 terms · Flashcards for McDougal Littell Geometry Chapter 10

### circle

the set of all points in a plane that are equidistant from a given poing, called the center of the circle.

### common external tangent

a common tangent that does not intersect the segment that joins the centers of the circles.

### common internal tangent

a common tangent that intersects the segment that joings the centers of the circles.

### theorem 10.1

in a plane, a line is tangent to a cirlce if and only if the line is perpendicular to a radius of the circle at its endpoint on the circle.

### minor arc

if the measure of angle APB is less than 180 degrees, then the portion of the circle included between points A and B form this

### major arc

this starts and ends with points A and B but it is the arc that lies in the exterior of angle APB.

### arc addition postulate

the measure of an arc formed by two adjacent arcs is the sum of the measures of the 2 arcs

### congruent arcs

the arcs are congruent if they have the same measure and they are arcs of the same circle or of congruent circles.

### theorem 10.3

in the same circle, or in congruent circles, 2 minor arcs are congruent if and only if their corresponding chords are congruent.

### theorem 10.4

if one chord is a perpendicular bisector of another chord, then the first chord is a diameter.

### theorem 10.5

if a diameter of a circle is perpendicular to a chord then the diameter bisects the chord and its arcs.

### theorem 10.6

in the same circle, or in congruent circles, two chords are congruent if and only if they are equidistant from the center.

### inscribed angle

an angle whose vertex is on a circle and whose sides contain chords of the circle.

### intercepted arb

the arc that lies in the interior of an inscribed angle and has endpoints on the angle.

### theorem 10.7

the measure of an inscribed angle is one half the measure of its intercepted arc.

### theorem 10.8

if 2 inscribed angles of a circle intercept the same arc, then the angles are congruent.