# 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.

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: Concurrency of angular bisectors.ggb

### 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 ?