What are you going
to identify the position
of two lines
to define an angle
To estimate the
measure of an angle
to measure an angle
to draw an angle
to determine types of
to describe the angle
formed by two lines
cut by a transversal
• parallel lines
• skew lines
• supplementary angles
• corresponding angles
• alternate interior
• alternate exterior
• consecutive interior
Position of Two Lines
Look at Figure 7.1(a) and 7.1(b)
on the right. What is the
relationship between the two
Look at Figure 7.1(b)
are two parallel segments.
Why? Find other pairs of parallel segments.
Segments AB and DC are parts of lines l and m, which
are infinite in length as shown above. The lines l and m
can also be denoted as AB and CD .
The segments AB and AD are two intersecting segments.
Why? Find other pairs of intersecting segments.
The segments AB and FG are two skew segments (neither
parallel nor intersecting). Why? Find other pairs of skew
Mathematics for Junior High School Year 7 / 277
Definition of an Angle
In the elementary school you had learned the definition of
an angle. To remind you, look and do the activity as shown in
Draw the position of
the straw on a sheet of
Take a straw and then
Figure 7.2(b) is an example of an angle. In Mathematics, an
angle is formed by two rays the initial points of which coincide,
as shown in the following figure.
Legs, BA and BC
Area of angle
Based on Figure 7.3, components of an angle are: two sides
(legs) of the angle, the vertex of