Measures in triangle

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The components that make a triangle are investigated. Measuring these components gives a better understanding of properties of triangles. Relation between these components are conceptualized.


To learn the different measurements in a triangle and the associated properties

Estimated Time

Prerequisites/Instructions, prior preparations, if any

Prior knowledge of point, lines, angles, parallel lines

Materials/ Resources needed

  • Digital : Computer, geogebra application, projector.
  • Non digital : Worksheet and pencil.
  • Geogebra files : Measures in triangle.ggb

Download this geogebra file from this link.

Process (How to do the activity)

  • Show the Geogebra file and ask students to record the values of angles and sides that are seen and ask if there is any connection between the side and the angle
  • What is the sum of the angles in a triangle?
  • Students make triangles picking any three strings from the set of strings they have been given. Is there any time when a triangle is not possible?
  • Side of triangle
  • Use the file “Measures in a triangle.ggb”. This file can be used to help students’ conception of triangle in a generalized manner. This file can be used to illustrate revise the points about vertically opposite angles, adjacent angles etc,. Help students identify the triangle. (Use the transaction notes for this file as needed)
  • Ask the students to make another 3 triangles from the strings they have been given. Students should make a triangle in which all angles are acute and one in which one angle is obtuse. Use the following Geogebra file for types of triangles by angle.Have the students explore the types of angles in a triangle.
  • Ask the students to make another set of two or three triangles with the strings they have been given. Is there anything you can say about the sides of the triangle? Show the Geogebra file called Types of triangle by sides.


  • Have the students been able to measure? Do they have an idea of what are the measurements possible?
  • Have they been able to generalize the sum of angle?
  • Have they been able to generalize any result about sides of a triangle?
  • Are the students able to recognize a triangle in a general manner?
  • Are they able to recognize types of triangles?