Construction of a triangle with 3 sides

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Investigating formation of a unique triangle with the given parameters as the three sides. Constriction follows SSS congruence rule.


  • To construct a triangle for given 3 sides
  • To show formation of different types of triangles when sides are varied
  • To show changes in angles when sides are varied.
  • To show possibility of formation of a triangle 

Estimated Time

30 minutes

Prerequisites/Instructions, prior preparations, if any

Prior understanding of point, lines and angles, elements of triangle, properties of triangle

Materials/ Resources needed

Download this geogebra file from this link.

Process (How to do the activity)

  • Use the geogebra file to demonstrate how to construct a triangle if three sides of a triangle are given
  • Students can be asked for a given any one side how many triangles are possible.
  • How will you  draw the second side? Where will you fix the position of the second side?
  • How will you draw the third side? How can you fix the position third side?
  • For what measurement of sides the triangle is not possible.
  • Vary the sliders to observe the changes reflected in the triangle.
  • Make different types of triangles with respect to  sides by changing the sliders.
  • Challenge them to make
    • Isosceles right angled triangle,
    • Equilateral triangle including right angle or obtuse angle
  • Note the measure of sides in the worksheet

Work sheet

Side1 Side2 Side3 Side1+ Side2 > Side 3 Side2 + Side 3 > Side 1 Side1+ Side3 > Side 2 YourObservations

Evaluation at the end of the activity

  • Can you construct a triangle for any given sides?
  • For given 3 sides how many triangles are possible?
  • Will the triangle formed change if the order of sides taken for construction is changed?

**Actual construction (using robocompass)