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Angle Measure

- Degree A unit of measure resulting from the

division of the circumference of a circle into

360 parts. - Ray A part of a line that has one endpoint and

extends infinitely in one direction. Rays are

named by stating the endpoint first and then any

other point on the ray. Rays are labeled using a

one-directional arrow.

Angle Measure

- Opposite Rays Two rays determined by choosing a

point on a line. Thus, these rays share a common

endpoint and are collinear. - Angle A geometric figure formed by two

noncollinear rays that have the same endpoint. - Sides The rays that form the angle.
- Vertex The common endpoint.

Angle Measure

- Naming an Angle An angle is named using either

its vertex, its vertex and a point on each ray,

or a numerical label. - Labeling an Angle When labeling an angle, use

the ? symbol in front of the angles name. When

mentioning an angles measure, use an m in front

of the ? to indicate measure.

Example 4-1d

Answer ?1, ?2, ?3, and ?RXB or ?RXN

Answer ?AXB, ?AXN, ?NXA, ?BXA

Angle Measure

- Interior of an angle A point is in the interior

of an angle if it does not lie on the angle

itself and it lies on a segment with endpoints

that are on the sides of the angle. - Exterior of an angle A point is in the exterior

of an angle if it is neither on the angle itself

nor in the interior of the angle.

Angle Measure

- Acute angle - An angle is acute if and only if

its measure is between 0 and 90 degrees. - Right angle - An angle is a right angle if and

only if its measure equals 90 degrees. - Obtuse angle - An angle is obtuse if and only if

its measure is more than 90 degrees and less than

180 degrees.

Example 4-2d

Answer 150, obtuse

Answer 90, right

Answer 30, acute

Angle Measure

- Congruent Angles Angles that have the same

measure. - Angle Bisector A ray that divides an angle into

two congruent angles.