Classify Types of TrianglesUnit of Study 10: Plane ShapesGlobal Concept Guide: 4 of 4

Content DevelopmentStudents 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.

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

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.

Classifying based on sides

Equilateral Scalene IsoscelesA triangle that has all equal

sides.

A triangle with no equal sides

A triangle with two equal

sides.

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

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 9.7 403B