Your device is currently offline. You can view downloaded files in My Downloads.

Lesson Plan

6. Identify similarity in triangles using angles (FP)

teaches Common Core State Standards CCSS.Math.Content.8.G.A.5 http://corestandards.org/Math/Content/8/G/A/5
teaches Common Core State Standards CCSS.Math.Practice.MP6 http://corestandards.org/Math/Practice/MP6
Quick Assign

You have saved this lesson!

Here's where you can access your saved items.

Dismiss

Card of

or to view additional materials

You'll gain access to interventions, extensions, task implementation guides, and more for this lesson.

Lesson objective: Fluently determine similarity in triangles by identifying equivalent relationships of the sides or identifying two pair of congruent corresponding angles.

This lesson helps to build fluency with the attributes of similar shapes. Triangle side lengths and angles are used here because similarity of triangles can be determined from two pairs of corresponding angles being congruent or a consistent scale factor. This work develops students' understanding that a triangle resulting from a series of transformation (dilations, rotations, reflections, or translations) is similar to the original triangle because two pairs of corresponding angles are congruent.

Students engage in Mathematical Practice 6 (attend to precision) as they use precise measurements when discussing similar triangles. Students should not assume shapes are similar without either identifying angles are congruent or given the shapes are similar.

Key vocabulary:

  • acute triangles
  • corresponding angles
  • equilateral triangles
  • isosceles triangles
  • obtuse triangles
  • right triangles
  • scalene triangles
  • similarity
  • transformation
  • vertical angles

Special materials needed:

  • grid paper
  • protractors
  • rulers
Related content

Appears in

Understanding similarity

Provide feedback