8.G.A.5

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- 8.G.A.1Verify experimentally the properties of rotations, reflections, and translations:
- 8.G.A.2Understand that a two-dimensional figure is congruent to another if the second can be obtained from the first by a sequence of rotations, reflections, and translations; given two congruent figures, describe a sequence that exhibits the congruence between them.
- 8.G.A.3Describe the effect of dilations, translations, rotations and reflections on two-dimensional figures using coordinates.
- 8.G.A.4Understand that a two-dimensional figure is similar to another if the second can be obtained from the first by a sequence of rotations, reflections, translations, and dilations; given two similar two-dimensional figures, describe a sequence that exhibits the similarity between them.
- 8.G.A.5Use 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.

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## 8.G.A.5

## 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)

### PTA (Parallel Lines, Transversals and Angles)

Geometry »
Unit: Line-sanity!

Geometry »
Unit: Line-sanity!

Big Idea:

#### Students will draw and measure to discover relationships of angles formed by parallel lines cut by a transversal.

Standards:

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(22)

Resources
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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

### Super Practice with Angles and Algebra

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

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

8th Grade Math »
Unit: Congruence and Similarity

8th Grade Math »
Unit: Congruence and Similarity

### 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

### Special angle pairs

8th Grade Math »
Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES

8th Grade Math »
Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES

### The Triangle Sum Setup

8th Grade Math »
Unit: Congruence and Similarity

8th Grade Math »
Unit: Congruence and Similarity

### Transversals 1

8th Grade Math »
Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES

8th Grade Math »
Unit: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES

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

8th Grade Math »
Unit: Congruence and Similarity

8th Grade Math »
Unit: Congruence and Similarity

### Defining Key Angle Relationships

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

### Angles and Algebra

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

### Why Do Triangles Have 180 Degrees?

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

### Why Are Vertical Angles Equal?

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

8th Grade Math »
Unit: Lines, Angles, and Algebraic Reasoning

### 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

### 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

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