Download Section 1 Section 1 – 6 Measuring Angles Section 1 Section 1 – 6

8/29/2011
ANGLE
Section 1 – 6
Measuring Angles
Learning Targets:
1. To be able to find the measures of angles
and classify them.
2. To be able to identify special angle pairs.
Examples
• An angle is formed by two rays with
the same endpoint.
– Rays act as the SIDES of the angle.
– The endpoint is the VERTEX of the
angle.
Protractor Postulate
- Let two rays act as opposite rays in a
plane; aligned with the straightedge
of your protractor. All of the rays
that can be drawn along these
opposite rays, sharing the same
endpoint, can be paired with the real
numbers from 0 to 180 to indicate
angle measure.
Classifying Angles
• Acute Angle
– Between 0 and 90 degrees
• Right Angle
– Exactly 90 degrees
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Classifying Angles
• Obtuse Angle
– Between 90 and 180 degrees
Vocabulary
• Congruent Angles
– Angles that have the same measure.
• Vertical Angles
– Two angles whose sides are opposite
rays.
• Straight Angle
– Exactly 180 degrees
• Adjacent Angles
– Two coplanar angles with a common side,
a common vertex and NO common
interior points.
Vocabulary
• Complementary Angles
– Two angles whose measures have a sum
of 90 degrees.
• Supplementary Angles
– Two angles whose measures have a sum
of 180 degrees.
Angle Addition Postulate
• If a point lies in the interior of an
angle, then the measure of the two
angles formed equals the measure of
the original angle.
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