Angles (elementary)

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Students learn about classifying angles by their measure.


Upon completion of this lesson, students will:

  • have learned what determines whether an angle is acute, obtuse, or right

Standards Addressed:

Textbooks Aligned:

Student Prerequisites

  • Technological: Students must be able to:
    • perform basic mouse manipulations such as point, click and drag
    • use a browser for experimenting with the activities

Teacher Preparation

The teacher will need:

  • access to a browser

Key Terms

acute angleAn angle whose measure is less than 90 degrees
obtuse angleAn angle whose measure is greater than 90 degrees
right angleAn angle of 90 degrees

Lesson Outline

  1. Focus and Review

    Review any previously learned information regarding angles.

  2. Objectives

    Let the students know what they will be doing and learning today. Say something like this:

    • Today, class, we are going to learn about angles.
    • We are going to learn about ways to classify angles:
      • Acute Angle
      • Obtuse Angle
      • Right Angle

  3. Teacher Input

    Lead the class in a short discussion about angles.

  4. Guided Practice

    • Open the Angles applet, show the students how it works, and emphasize that they can ignore the "Two angles are" drop-down menu.
    • Ask students to point out which angles are acute, obtuse, and right.
    • Show the Angles Worksheet to students and explain that they are supposed to write the names of all the angles that are acute in the acute column, etc.

  5. Independent Practice

    • Have students open the Angles Applet.
    • Have students work in pairs to complete the Angles Worksheet.
    • Remind students that they must complete at least 10 computer generated problems from the applet.

Alternate Outline

If only one computer is available, the activity can be rearranged in the following ways:

  • One computer could be connected to a projector in order to display each of the ten problems that the students would complete individually.
  • Ten different problems could be printed off to provide students with a paper reference to use while completing the worksheet.

Suggested Follow-Up

For advanced students, consider using the Angles Lesson.

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