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# Prove interior angles of a triangle using transversals

Lesson 5 of 9

## Objective: SWBAT prove that the interior angles of a triangle sum to 180 degrees, using transversals.

*75 minutes*

#### Warm Up

*10 min*

Each day, students complete a warm-up that usually consists of spiraling the previous day's material, in addition to older material. Warm-up problems also sometimes extend lessons that students have encountered before to more unfamiliar contexts. Today's warmup can be found in 7 - 5 WU95.

For a video narrative about how I structure each lesson, and how the warm-up fits in, click here.

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#### Huddle

*10 min*

I push kids to come up to the board to prove that the interior angles of a triangle is 180 degrees, using transversals. I have include two student proofs on video below and a third can be seen see students actually doing this on video. The Student Work file contains several examples of the students' written proofs.

**Student Proof #1**

Student Proof #2

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#### Homework

*15 min*

Homework 7 - 5 HW95 is to be completed at home and should take students approximately 15 minutes.

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- UNIT 1: FLUENCIES AND THE LANGUAGE OF ALGEBRA
- UNIT 2: SOLVING LINEAR EQUATIONS
- UNIT 3: INTRODUCTION TO FUNCTIONS
- UNIT 4: INTERPRETING AND COMPARING LINEAR FUNCTIONS
- UNIT 5: SYSTEMS OF LINEAR EQUATIONS
- UNIT 6: EXPONENTS AND SCIENTIFIC NOTATION
- UNIT 7: PARALLEL LINES, TRANSVERSALS, AND TRIANGLES
- UNIT 8: CONGRUENCE AND SIMILARITY THROUGH TRANSFORMATIONS
- UNIT 9: PATTERNS OF ASSOCIATION IN BIVARIATE DATA
- UNIT 10: SLOPE REVISITED
- UNIT 11: VOLUME OF CYLINDERS, CONES, AND SPHERES
- UNIT 12: POLYNOMIALS AND FACTORING
- UNIT 13: QUADRATIC FUNCTIONS

- LESSON 1: Special angle pairs
- LESSON 2: Transversals 1
- LESSON 3: Transversals 2
- LESSON 4: Practice transversals and blast from the past
- LESSON 5: Prove interior angles of a triangle using transversals
- LESSON 6: Prove interior angles of triangles 2
- LESSON 7: Prove exterior angles of triangle
- LESSON 8: Prove exterior angles of triangles 2
- LESSON 9: Arrange 3 copies to prove interior angles of triangles