Construction of a triangle with side, angle and sum of other two sides

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The triangle inequality states that the sum of the lengths of any two sides of a triangle must be greater than or equal to the length of the third side. Construction of a triangle with given parameters sum of two sides and an angle follows SAS congruence rule.


To construct a triangle with side, angle and sum of other two sides

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 slider to set the base and the given angle
  • The difference of the other two sides is marked using the slider
  • Follow the steps for construction – step1, step2
  • Students can vary the sliders to observe the changes reflected in the triangle.

Evaluation at the end of the activity

  • When does the triangle not form?