Name and classify angles.

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Objectives
Name and classify angles. Measure and construct
angles and angle bisectors.
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An angle is formed by two rays, or sides, with a
common endpoint called the vertex (plural
vertices).
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The set of all points between the sides of the
angle is the interior of an angle. The exterior
of an angle is the set of all points outside the
angle.
Angle Name ?R, ?SRT, ?TRS, or ?1
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Check It Out! Example 1
Write the different ways you can name the angles
in the diagram.
?RTQ, ?T, ?STR, ?1, ?2
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Congruent angles are angles that have the same
measure. In the diagram, m?ABC m?DEF, so you
can write ?ABC ? ?DEF. This is read as angle
ABC is congruent to angle DEF. Arc marks are
used to show that the two angles are congruent.
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Example 2 Using the Angle Addition Postulate
m?DEG 115, and m?DEF 48. Find m?FEG
m?DEG m?DEF m?FEG
? Add. Post.
115? 48? m?FEG
Substitute the given values.
Subtract 48 from both sides.
67? m?FEG
Simplify.
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Example 3
m?XWZ 121 and m?XWY 59. Find m?YWZ.
m?YWZ m?XWZ m?XWY
? Add. Post.
m?YWZ 121? 59?
Substitute the given values.
m?YWZ 62?
Subtract.
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Example 4 Finding the Measure of an Angle
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Example 5
Find the measure of each angle.
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Lesson Quiz Part I
Classify each angle as acute, right, or obtuse.
1. ?XTS
acute
right
2. ?WTU
3. K is in the interior of ?LMN, m?LMK 52, and
m?KMN 12. Find m?LMN.
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Lesson Quiz Part II
4. m?WYZ (2x 5) and m?XYW (3x 10). Find
the value of x.
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