Angle Measure

1
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.

2
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.

3
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.

4
Example 4-1d
Answer ?1, ?2, ?3, and ?RXB or ?RXN
Answer ?AXB, ?AXN, ?NXA, ?BXA
5
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.

6
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.

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Example 4-2d
Answer 150, obtuse
Answer 90, right
Answer 30, acute
8
Angle Measure

• Congruent Angles Angles that have the same
  measure.
• Angle Bisector A ray that divides an angle into
  two congruent angles.