Target

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Target
Lesson 4-2 Angles of Triangles
TARGETS

• Apply the Triangle Angle-Sum Theorem.
• Apply the Exterior Angle Theorem.

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Tri angle sum th
LESSON 4-2 Angles of Triangles
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Ex1 Tri Ang Sum Th
LESSON 4-2 Angles of Triangles
Use the Triangle Angle-Sum Theorem
EXAMPLE 1
SOFTBALL The diagram shows the path of the
softball in a drill developed by four players.
Find the measure of each numbered angle.
WORK REASONS
Triangle Angle-Sum Th.
Vertical angles
?1 ? ?2 m?1 m?2 63 m?2
Def of Congruent
Substitution
Triangle Angle-Sum Th.
Check The sums of the measures of the angles in
each triangle should be 180. m?1 43 74 63
43 74 or 180? m?2 m?3 79 63 38 79
or 180?
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Ex Angle The
LESSON 4-2 Angles of Triangles
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Ex2 Ext Ang Th.
LESSON 4-2 Angles of Triangles
Use the Exterior Angle Theorem
EXAMPLE 2
GARDENING Find the measure of ?FLW in the fenced
flower garden shown.
WORK REASONS
m?LOW m?OWL m?FLW Exterior Angle
Theorem x 32 2x 48 Substitution 32
x 48 80 x
Answer So, m?FLW 2(80) 48 or 112.
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Ex3 Right Tri
LESSON 4-2 Angles of Triangles
Find Angle Measures in Right Triangles
EXAMPLE 3
Find the measure of each numbered angle.
WORK REASONS
Complementary
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Ex3 Right Tri
LESSON 4-2 Angles of Triangles
Find Angle Measures in Right Triangles
EXAMPLE 3
Find the measure of each numbered angle.
WORK REASONS
Triangle Sum Theorem
132 m?4 180
m?4 48
m?5 143 180
m?5 49