Jeff
Li MTP
KIPP Infinity Charter School,
NEW YORK,
NY

8th Grade Math :
Unit #7 - PARALLEL LINES, TRANSVERSALS, AND TRIANGLES :
Lesson #5

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

1 Warm Up -
10 minutes

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.

resources

7 - 5 WU95 Prove angle sum and exterior angles of a triangle using transversals.pdf

https://betterlesson.com/lesson/resource/2015718/7-5-wu95-prove-angle-sum-and-exterior-angles-of-a-triangle-using-transversals-pdf
7 - 5 WU95 Prove angle sum and exterior angles of a triangle using transversals.docx

https://betterlesson.com/lesson/resource/2015719/7-5-wu95-prove-angle-sum-and-exterior-angles-of-a-triangle-using-transversals-docx
2 Play of the Day -
40 minutes

7 - 5 VN95 Prove interior angles of triangles using transversals.MOV

https://betterlesson.com/lesson/section/6261/prove-interior-angles-of-a-triangle-using-transversals
resources

7 - 5 POTD95 Prove angle sum and exterior angles of a triangle using transversals.docx.doc.pdf

https://betterlesson.com/lesson/resource/2032922/7-5-potd95-prove-angle-sum-and-exterior-angles-of-a-triangle-using-transversals-pdf
7 - 5 POTD95 Prove angle sum and exterior angles of a triangle using transversals.docx.doc.docx

https://betterlesson.com/lesson/resource/2015717/7-5-potd95-prove-angle-sum-and-exterior-angles-of-a-triangle-using-transversals-docx
3 Huddle -
10 minutes

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

resources

Student work - proofs of sum of interior angles of a triangle with transversals.pdf

https://betterlesson.com/lesson/resource/2015517/student-work-proofs-of-sum-of-interior-angles-of-a-triangle-with-transversals-pdf
4 Homework -
15 minutes

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

resources

7 - 5 HW95 Prove angle sum of triangles.docx

https://betterlesson.com/lesson/resource/2015520/7-5-hw95-prove-angle-sum-of-triangles-docx
7 - 5 HW95 Prove angle sum of triangles.docx.doc.pdf

https://betterlesson.com/lesson/resource/2015715/7-5-hw95-prove-angle-sum-of-triangles-docx-doc-pdf