Education Technology

Right Triangles are Cool Because of Pythag's Rule

Published on 06/09/2008

Activity Overview

In this activity, students use the Geoboard to determine the length of the sides of a right triangles.

Before the Activity

  • Start the Geoboard App and format it
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 85 - 91 from the attached PDF file for your class
  • During the Activity

    Distribute the page to the class.

    Follow the Activity procedures:

  • Draw a right triangle with leg lengths of 1 unit and draw squares on each side of the triangle


  • Draw right triangles with the different leg lengths given in the table
  • Draw surrounding squares and record areas of the squares
  • Find the relationship between the areas of the squares
  • Understand the Pythagorean Theorem that states - the sum of the square of the length of the legs is equal to the square of the length of the hypotenuse in a right triangle
  • Draw a right angle triangle with sides 3 and 4 and find the length of the hypotenuse
  • Note the length is 5 units


  • Draw four right triangles with length of legs that are different from those used earlier
  • Enter leg lengths, hypotenuse length, leg length squared, and hypotenuse squared in different columns
  • Find the relationship between the leg length squared and the hypotenuse squared
  • Observe that the sum of the leg length squared is equal to the hypotenuse squared and the Pythagorean Theorem is valid in right triangle is A2 + B2 = C2
  • Given the length of the sides of a triangle identify the triangle as acute, right, or obtuse
  • If A2 + B2 > C2 then the triangle is an acute triangle
  • If A2 + B2 = C2 then the triangle is a right triangle
  • If A2 + B2 < C2 then the triangle is an obtuse triangle
  • After the Activity

    Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary