# 3. Angles and sides of polygons (A)

teaches Common Core State Standards CCSS.Math.Content.4.G.A.1 http://corestandards.org/Math/Content/4/G/A/1
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

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Lesson objective: Apply knowledge of points, lines, line segments, rays, and angles to reason about shapes.

This lesson provides an opportunity for students to apply their knowledge and understanding of the building blocks of geometry to a  mathematical situation. Students are asked to notice a pattern or relationship between the number of line segments and angles in polygons.

Key Concept students will use:

•  understanding that points, lines, line segments, and rays have specific properties that are maintained when combined to make geometric figures. One of these new figures, an angle, is a geometric figure that is created wherever two rays share a common endpoint.

Skills students will use:

• Exploring standard units of length; (Grade 2, Unit 2)
• Understanding unit fractions; (Grade 3, Unit 4)
• Solving problems involving shapes; (Grade 3, Unit 13)

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they analyze relationships among goemetric figures to look for structures to draw conclusions about the number of sides and angles in polygons.

Key vocabulary:

• angle
• attribute
• closed
• endpoint
• figure
• line
• line segment
• point
• polygon
• ray
• side
• vertex

Special materials needed (optional):

• geoboards and rubber bands
• plastic polygon shapes
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