Apply Triangle Sum Properties

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Section 4.1

• Apply Triangle Sum Properties

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Homework

• Pg 221 17-19, 34, 48 (only prove 48)

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Vocabulary

• Scalene no congruent sides
• Isosceles - two congruent sides
• Equilateral three congruent sides
• Acute three acute angles
• Right one right angle
• Obtuse one obtuse angle
• Equiangular three congruent angles
• Interior Angles angles on the inside of a
  polygon
• Exterior Angles angles that form a linear pair
  with Interior Angles

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Theorem 4.1 Triangle Sum Theorem

• The sum of the measure of the interior angles of
  a triangle is 180.

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Theorem 4.2 Exterior Angle Theorem

• The measure of an exterior angle of a triangle is
  equal to the sum of the measures of the two
  nonadjacent interior angles.

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Corollary to the Triangle Sum Theorem

• The acute angles of a right triangle are
  complementary.

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Prove Triangle Sum Theorem
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Find an angle measure
Find m? JKM.
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Example
Find the measure of each interior angle of
ABC, where m A x , m B 2x , and m
C 3x.