1. Classify Types of Triangles
Unit of Study 10: Plane Shapes
Global Concept Guide: 4 of 4

2. Content Development
Students need to understand there are 3 different ways to categorize triangles based on sides: Equilateral, Isosceles, Scalene. There are also 3 different ways to classify shapes based on angles: Acute, Right, Obtuse Students should understand that the green triangle from the pattern block set is not the only type of triangle and that a triangle is defined as any closed figure that is made up of 3 line segments that meets exactly at their vertices. 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.

3. Day 1 How can you describe a triangle?
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.)
Have students sort the triangles and record the attributes in which they sorted them.
Discuss attributes
Have students build triangles using Anglegs and Geoboards

4. Day 2 How can you compare and classify triangles?
Students apply their understanding of triangles from Day 1 to classifying triangles on Day 2.
Have students discuss the attributes of the shapes and create definitions based on the attributes.
Have students classify shapes
based on the student generated
definitions.

5. Classifying based on sides
Equilateral
Scalene
Isosceles
A triangle that has all equal sides.
A triangle with no equal sides
A triangle with two equal sides.

6. Classifying based on angles
Acute
Obtuse
Right
A triangle that has all acute angles
A triangle with one obtuse angle.
A triangle with one right angle

7. Enrich/Reteach
For students who are struggling with this concept, use the Reteach Activity on 399B. Also, the lesson 9.6 Reteach on R82 can be used to help students develop an understanding of the types of triangles.
For students who need extensions, give them a variety of riddles. The Enrich activity on E83 can be used as well as the Enrich Activity Lesson B