Construction of a triangle with 3 sides
This activity shows construction of a triangle when the three sides of a triangle are known. The construction is based on SSS congruence rule. Congruent triangle is formed irrespective of any side of the three given sides is taken to begin the construction. The activity also helps in exploring if a triangle is formed for any given three sides.
Objectives
- 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
- Digital : Computer, geogebra application, projector.
- Non digital : Worksheet and pencil
- Geogebra files : "Triangle construction (3sides)"
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?