Measuring Segments

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Measuring Segments Angles
During todays lesson, you will find the measures
of angles.
.
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ANGLE VOCABULARY
An angle (?) is formed by two rays with the same
endpoint.
The rays are the sides of the angles and the
endpoint is the vertex.
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Angles can be named in 3 different ways
1. Using 3 points ?TBQ or ?QBT 2. Using
the vertex ?B 3. Using a number inside the
angle ?1
ALERT! When the vertex is shared, you cannot
use it to name an angle.
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Measuring Angles

• The size of an angle is the amount of turn
  necessary to rotate one ray to fit on the other
  ray. You measure this rotation in units called
  __________________.

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An acute angle has a measure

• between 0 and 90.

A right angle has a measure
a measure of exactly 90.
An obtuse angle has a measure
a measure between 90 and 180.
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A straight angle has a measure
of exactly 180.
Congruent angles are
two angles with the same measure.
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Notation for congruent angles

Use ?ABC ? ? DEF when referring to the actual
angles.
Use m?ABC m? DEF when referring to the measure
of the angles.
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Measuring Angles

Place the center mark of the protractor on the vertex of the angle. Rotate the zero-edge of the protractor to line up with one side of the angle. Read the size of the angle on the protractors side where the other angle crosses.
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Practice Measuring Angles
46?
89
120
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Final Checks for Understanding

• Name four ways by which we classify angles based
  upon their degree measure.
• Use the diagram below to answer the following
  questions
• a. Is ?DEF ? ?FEG?
• b. Is Is ?DEF ? ?FEG?
• c. Are ?DEF and ?FEH
• adjacent?

F G
45 45
D E H