Exterior Angles of a Triangle Inquiry Activity

Math Giraffe
Grade Levels
PDF (4 MB|7 plus answer keys & directions)
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This activity guides students to develop rules for the properties of exterior angles of a triangle. Through inquiry-based learning, students are able to discover the theorem on their own and therefore understand the concept better and can remember why it works. The activity uses critical thinking. Students write their observations in complete sentences. The activity introduces students to the concepts of an "exterior angle" as well as "remote interior angles."

Here's what's included:
- A half-page differentiated warm-up to review prior knowledge
- A 2-page guided inquiry worksheet for discovering Exterior Angles Theorem
- A quick hands-on activity with exterior angles of a triangle
- A small exit ticket plus an organizer to record the rule with a diagram plus the student’s own words and examples
- Algebra application problems
- Answer keys

*** This activity is also included in a larger DISCOUNTED bundle:
Triangles Bundle

Take a look at the preview file for more information.

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Lesson Pack: Transversals
Total Pages
7 plus answer keys & directions
Answer Key
Teaching Duration
1 hour
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to see state-specific standards (only available in the US).
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.


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