Describe and Classify Polygons Unit of Study 10: Plane Shapes Global Concept Guide: 2 of 4

Content Development Students need opportunities to define shapes based on attributes. Example: a triangle is any closed figure made up of three line segments that connect only at vertices. Students should explore a variety of shapes, sort them based on attributes, and name them based on their attributes. Vocabulary and attributes should be heavily emphasized throughout this Unit of Study. It is important to focus on the properties of the figures rather than on simple identification.

Day 1  How do you use attributes of plane figures to name polygons?  Show various examples of triangles and ask students to notice what all the shapes have in common (all closed figures, all made up of 3 line segments, all have 3 vertices etc.)  Using STUDENT generated definitions, name the shapes. Have students use Geoboards or Anglegs to create a shape that fits the definition of the polygon.  Repeat using quadrilaterals, pentagons, hexagons, heptagons, octagons, decagons etc.  The book, The Greedy Triangle is EXCELLENT for this lesson.  Once students learn to name polygons use the Alphabet sort.

Day 2  How do you describe and classify angles?  Start with “Square angles” (right angles) Glue two popsicle sticks together to make a 90 degree angle. Have students use this referent to travel around the room and find angles that are exactly “square” (right angles) and angles that are larger and smaller. They will begin to see that there are angles that larger than their square angle and angles that are smaller than their square angles. This is a great time to introduce types of angles (acute, right, obtuse).  Use the classifying angles activity posted under Lesson Ideas to help students classify angles.

Day 3  How do you identify pairs of parallel sides in polygons?  Discuss what a “pair” is. Make connections to real world, pair of shoes (you need two shoes to make a pair). A pair of socks (you need two socks to make a pair etc.)  Anglegs are an excellent resource to use with this lesson.  Incorporate the vocabulary: parallel, perpendicular, intersecting into instruction.  Have students identify types of lines in the real world.

Enrich/Reteach  For students who are struggling with this concept, use Geoboards and Anglegs to have students build polygons and explore different angles.  For students who need extensions, give them a variety of riddles. The Enrich activity on p. 385B. Students then choose another, polygon, angle, or type of line and write another riddle about the attributes to help students pick out what they are referring to.

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