In these lessons, we will learn

Related Topics: More Geometry Lessons

An angle bisector is a straight line that divides the angle into two equal parts.

The following video shows how to draw an angle bisector using a compass and a straight edge.

1. Place compass point on the vertex, and draw an arc across each ray.

2. Place the compass on each arc intersection and draw a further pair of arcs which intersect each other.

3. Use a straight edge to connect the intersection point to the vertex.
The following video shows how to bisect a given angle using only a compass and straightedge.

### Use angle bisector to construct angles

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- how to construct an angle bisector of a given angle.
- how to use an angle bisector to construct some angles for example, 90 degrees, 45 degrees, 60 degrees, 30 degrees, 120 degrees, 135 degrees, 15 degrees.

Related Topics: More Geometry Lessons

An angle bisector is a straight line that divides the angle into two equal parts.

* Example : *Construct an angle bisector for the following angle:

*Solution: *

**Step 1 :** Put the sharp end of your compasses at point *B* and make one arc on the line *BC* (point *S*) and another arc on line *AB *(point *T*).

**Step 2 **: Without changing the width of your compasses, put the sharp end of the compasses at *S* and make an arc within the lines *AB* and *BC.* Do the same at *T* and make sure that the second arc intersects the first arc.

**Step 3 : **Draw a line from point *B* to the points of intersection of the 2 arcs. This line bisects .

1. Place compass point on the vertex, and draw an arc across each ray.

2. Place the compass on each arc intersection and draw a further pair of arcs which intersect each other.

3. Use a straight edge to connect the intersection point to the vertex.

We can use the angle bisector to construct some other angles from existing angles.

* Example*

A 30˚ angle can be obtained by bisecting a 60˚ angle.

A 15˚ angle can be obtained by bisecting a 30˚ angle.

A 45˚ angle can be obtained by bisecting a 90˚ angle.

A 22.5˚ angle can be obtained by bisecting a 45˚ angle.

*Example: *

The figure shows a point *A* on a straight line. Construct an angle of 45˚ at point *A*.

* Solution: *

Construct a 90˚ angle, and then construct an angle bisector to obtain a 45˚ angle.

The following video shows how to construct 30, 45, 60, 90, and 120 degree angles with a compass

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