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
 quadrilateral
 ray
 side
 vertex
Special materials needed (optional):
 geoboards and rubber bands
 plastic polygon shapes