2. DEFINITION and PARTS of an angle
The amount of turn between two straight lines that have a
common end point (the vertex).
3. USING A PROTRACTOR
Set the protractor so that:
The vertex of the angle match the protractor centre.
One angle arm should match the base line.
Read the score, this is the angle measure.
If the arms of the angles are too short...
Make them longer using a ruler and a pencil
5. CONSTRUCTING ANGLES
Let's construct a 45º angle:
1. Trace a line starting from point A.
2. Match point A with the protractor centre. The traced line
should coincide with the protractor base line.
3. Mark the 45º with a litle point using the pencil.
4. Join point A and the 45º mark with a line.
8. RELATION BETWEEN ANGLES
CONSECUTIVE: They have the vertex and one arm in common.
ADJACENT: They have the vertex and one arm in common and
they form a straight angle.
INVERSE: They have the vertex and the arms in common. They
are two intersecting lines.
10. LOOKING FOR THE BISECTOR
1. Put de compass needle on the angle vertex (O) and mark a
little arc on each angle arm (points A and B).
2. Mark an ark from point A.
3. With the same compass opening, mark another arc from
4. Join, using a ruler, the angle vertex (O) with the
crossing point of the arcs.
11. LINE BISECTOR
➲ The line bisector is the perpendicular line
that divides a segment in two equal parts
12. LOOKING FOR THE LINE BISECTOR
1. Open the compass (bigger than the half of the
segmet AB). Trace an arc from A.
2. With the same compass opening, trace an arc
from point B.
3. Join, using a ruler, the two meeing points.