## Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.

40 Lesson(s)

Geometry » Unit: Line-sanity!
Saratoga Springs, NY
Environment: Suburban

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### My Little Transversal: A multi-day project lesson

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
Environment: Urban

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### Super Practice with Angles and Algebra

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
Environment: Urban

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### Angles and Parallel Lines (Day 2 of 2)

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Orlando, FL
Environment: Urban

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### Prove interior angles of a triangle using transversals

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
New York, NY
Environment: Urban

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### Special angle pairs

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
New York, NY
Environment: Urban

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### Transversals 1

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
New York, NY
Environment: Urban

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### The Triangle Sum Setup

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Orlando, FL
Environment: Urban

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### Angles and Parallel Lines (Day 1 of 2)

8th Grade Math » Unit: Congruence and Similarity
8th Grade Math » Unit: Congruence and Similarity
Orlando, FL
Environment: Urban

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### Defining Key Angle Relationships

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
Environment: Urban

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### Angles and Algebra

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
Environment: Urban

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### Why Do Triangles Have 180 Degrees?

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
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### Why Are Vertical Angles Equal?

8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
8th Grade Math » Unit: Lines, Angles, and Algebraic Reasoning
New York, NY
Environment: Urban

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### Arrange 3 copies to prove interior angles of triangles

8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
8th Grade Math » Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
New York, NY
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### Discovering What it Means to be Similar Triangles

8th Grade Math » Unit: Linear Equations in two Variables
8th Grade Math » Unit: Linear Equations in two Variables
Bowling Green, KY
Environment: Suburban

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Common Core Math