Lesson 2 Ways to Look at Triangles

    • Let’s sort and analyze triangles.

Warm-up Number Talk: Sums and Products

Find the value of each expression mentally.

Activity 1 Triangle Hunt

Problem 1

From the set of triangle cards, find all the triangles that have each attribute. Record their letter names here.

No right angles

Parallel sides

Perpendicular sides

The same length for all sides

The same size for all angles

More than one right angle

More than one obtuse angle

More than one acute angle

Foldable into two equal halves

Problem 2

Choose one sentence to complete based on your work.

  1. I noticed that some triangles  …

  2. I noticed that all triangles  …

  3. I noticed that no triangles  …

Activity 2 The Right Kind of Triangle

  1. Identify all shapes that are right triangles. For each right triangle, mark the right angle with a small square.

    8 shapes
    8 shapes

  2. Explain why the other shapes are not right triangles.

Practice Problem

Problem 1

4 triangles, all have 3 sides of different length. A. 1 obtuse angle, 2 acute angles. B. 3 acute angles. C and D. 1 right angle, 2 acute angles.

  1. Which of the triangles are right triangles?

  2. Which of the triangles have an obtuse angle?

  3. Which of the triangles have 3 acute angles?