What is an Isosceles Triangle? - Definition, Properties & Theorem


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What is the measure of the indicated angle in the following illustration?

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1. If the area of the entire triangle below is 20 sq. in., what is the area of the shaded portion?

2. What is the perimeter of the isosceles triangle below?

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About This Quiz & Worksheet

Are you curious about what an isosceles triangle is? Use these tools to test your knowledge of triangles and to teach you important vocabulary terms that you will need to learn to pass the quiz.

Quiz & Worksheet Goals

This quiz and worksheet will test you on the following terms and topics:

  • Find the area of a triangle
  • Find angle measurements in isosceles triangles
  • Perimeter
  • Apex angles

Skills Practiced

You can use this interactive quiz and printable worksheet to practice the following skills:

  • Reading comprehension- ensure that you draw the most important information from the related lesson on isosceles triangles
  • Problem solving- use acquired knowledge to solve angle measurement practice problems
  • Knowledge application- use your knowledge to answer questions about apex angles

Additional Learning

Want to learn more about isosceles triangles? Then check out the accompanying lesson, What is an Isosceles Triangle? - Definition, Properties & Theorem. This lesson will cover the following objectives:

  • Define the terms congruent, bisection, and altitude
  • Understand what makes an isosceles triangle
  • Learn the formula to find the angles of an isosceles triangle