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Module 5 Lesson 1 Investigating Angles of Triangles (Please print the Learning guide notes that go with this lesson so that you can follow them and use them for reference on the assignments.)

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Triangles can be classified by sides AND by angles. When you look at the sides, you have 3 types of triangles: Scalene no sides are equal Isosceles 2 sides are equal Equilateral all 3 sides are equal

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When you look at the angles, you also have 4 types of triangles. Acute triangle all angles are less than 90 Obtuse triangle one angle is more than 90 Right triangle one angle is equal to 90 Equiangular triangle all angles have the same measure (that is 60)

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Classify each triangle (by sides and by angles) 3 4 5 A) B) C)

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Classify each triangle (by sides and by angles) 3 4 5 A) B) C) Obtuse and IsoscelesRight and scalene Equilateral and equiangular

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Triangle Angle Sum Theorem The sum of the interior angles of any triangle is 180 .

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Example Find x. x46 54 54 + 46 + x = 180 100 + x = 180 -100 ------------------- x = 80

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Another example Find m