Incentre of a triangle

As performed in real lab:

Material required:

Coloured papers, fevicol and a pair of scissors.


1. Cut an acute angled triangle from a colored paper and name it as ABC.

2. Fold along the vertex A of the triangle in such a way that the side AB lies along AC.

3. The crease thus formed is the angle bisector of angle A. Similarly, get the angle bisectors of angle B and C.   [Fig (a)].

4. Repeat the same activity for a obtuse angled triangle and right angled triangle. [Fig (b) and  (c)].


As performed in the simulator:

1.Select three points A, B and C anywhere on the workbench  to draw a triangle.

2. Depending on your points selection acute, obtuse or right angled triangle is drawn.

3. Now, click on each vertex of the triangle to draw its angle bisector. You can use the protractor to measure the angles .

4.Activity completed successfully. You can see the inference below.


                       Fig (a)                                                           Fig (b)                                        

                     Fig (c)



  •  We see that the three angle bisectors are concurrent and the point is called the incentre (O).
  •  We observe that the incentre of an acute, an obtuse and right angled triangle always lies inside the  triangle.