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Lesson Plan

7. Apply triangle angle sum to polygons (A)

teaches Common Core State Standards 8.8D
teaches Common Core State Standards G.5A
teaches Common Core State Standards CCSS.Math.Content.8.G.A.5
teaches Common Core State Standards CCSS.Math.Practice.MP3
teaches Common Core State Standards MAFS.8.G.1.5
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Lesson objective: Apply the triangle angle sum to polygons.

This lesson provides an opportunity for students to apply their knowledge and understanding of triangle angle sum to a mathematical situation. Students are asked to determine the interior angle sums of different polygons, analyze their results, and create a rule that determines the interior angle sum of any polygon. 

Key Concept students will use: 

  • The angle sum for any triangle is 180 degrees, and we can informally prove this using the relationships of angles.

Skills students will use:

  • angle sum of a triangle

Students engage in Mathematical Practice #3 (construct viable arguments and critique the reasoning of others) as they make conjectures about the polygon angle sum, justify their conclusions, and communicate them to others.

Key vocabulary: 

  • polygon
  • triangle angle sum

Special materials needed:

  • polygon templates (optional)
Related content

Appears in

Geometric relationships

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