Angular bisectors and incenter of a triangle

The intersecting point of three lines which are the bisectors of three angles of a triangle that is the incenter and it's properties are examined.

Objectives

Introduce angular bisectors in a triangle and their point of concurrence.

Estimated Time

40 minutes.

Prerequisites/Instructions, prior preparations, if any

Angles, angle bisectors , concurrent lines and triangles should have been covered.

Materials/ Resources needed

Digital resources: Laptop, projector and a pointer.

Geogebra file: This geogebra file was done by ITfC-Edu-Team.

Process (How to do the activity)

1. The teacher can use this geogebra file and ask the questions listed below.

• Developmental Questions;

1. What type of triangle is this ? Why ?
2. Identify the three angles.
3. What is an angle bisector ?
4. Identify the point of concurrence of angle bisectors ?
5. This point, called incentre of the triangle does its position change with the type of triangle ?
6. Identify the circle. What is its radius ? What can this radius be called ?
7. What is this circle called ?

• Evaluation:

1. What is incentre, inradius and incircle ?

• Question Corner:

1. What do you think would be the practical applications of the incentre and incircle ?