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Published byNoah Carson Modified over 9 years ago
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Lesson 3: (3.4) Parallel Lines and the Triangle Angle-Sum Theorem
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What are we learning? Purpose: Students will classify triangles, find the measures of their angles, and use exterior angles of triangles to solve problems. Evidence Outcome: Prove geometric theorems (lines, angles, triangles, parallelograms). Purpose (Relevancy): This concept is used to find the reclining angle of a lazy boy chair.
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Finding Angle Measures in Triangles
C 50° 35° A B Theorem 3-12: Triangle Angle-Sum Theorem: The sum of the measures of the angles of a triangle is 180.
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Finding Angle Measures in Triangles
C 50° 35° A B Find the measure of the three angles. Justify your work.
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Finding Angle Measures in Triangles
Find the values of x, y, and z. Justify your work. 39° 21° 65° x° y° z° F J H
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Finding Angle Measures in Triangles
B Find the values of x, y, and z. x° y° 62° z° 49° A C D
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Classifications of Triangles
Equiangular Acute Right Obtuse Equilateral Isosceles Scalene
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Classifications of Triangles
Classify the following triangles by their angles and sides. 3 in. 4 in. 5 in. 7 cm. 16 cm. 106° 37° Draw an equilateral right triangle. NOT POSSIBLE!!!
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Using Exterior Angles of Triangles
Exterior Angle of a Polygon: An angle formed by a side and an extension of an adjacent side. Remote Interior Angles Exterior Angle 1 2 3 Remote Interior Angles: The two nonadjacent interior angles corresponding to each exterior angle of a triangle.
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Using Exterior Angles of Triangles
1 2 3 Theorem 3-13: Triangle Exterior Angle Theorem: The measure of each exterior angle of a triangle equals the sum of the measures of its two remote interior angles.
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Using Exterior Angles of Triangles
100° x° 50° Find the measure of the x. Justify your work.
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Using Exterior Angles of Triangles
Find the values of w, x, y, and z. 97° x° y° 53° w° 86° z°
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Little More Practice Find the value of x. (80 – 2x)° (70 – 3x)°
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and the Triangle Angle-Sum Theorem
(3.4): Parallel Lines and the Triangle Angle-Sum Theorem HOMEWORK: (3.4): Pgs ; 2-26 even, 32, 34, 40 Homework Quiz Next Class! TERMS: equiangular Δ, acute Δ, right Δ, obtuse Δ, equilateral Δ, isosceles Δ, scalene Δ. Remember, with great power, comes great responsibility. -Uncle Ben
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