Page 305 - Math Smart - 7

Perpendicular lines and Prepare the following
materials for geometrical
parallel lines construction.
• sharp pencil
Perpendicular lines are straight lines that meet at a right angle. They are said to • eraser
be perpendicular to each other. The symbol 1 means 'is perpendicular to'. • ruler
• set square

Parallel lines are always the same distance apart. They will never meet no matter • protractor
how long they are drawn. They are said to be parallel to each other. The symbol // • compass
means 'is parallel to'. Arrow heads are used to show parallel lines.
Parallel lines Perpendicular lines

tL

The square indicates that line segment Try and Apply
The arrow heads indicate that line
AB is perpendicular to line segment CD.
segment AB is parallel to line segment CD.
We write this as AB 1 CD. 0 The diagram shows
We write this as AB H CD.
2 triangles. Name
s Figure 14.2 Notation for perpendicular lines and parallel lines 2 lines which are
perpendicular to AC.
Drawing perpendicular lines

In Stage 5, you learnt how to measure and draw right angles using a protractor.
Let us recall and learn to draw perpendicular lines using a protractor or a
set square.

Example 1

We can use a
Draw Z.xyz = 90°. Name a pair of perpendicular lines folded piece
of paper to
Solution check.
Place a protractor on line segment XY n
1 such that the centre of the protractor
is on point K Q Name all the pairs of
parallel lines in the
Adjust the position of the protractor
figure below.
such that its baseline is on line
segment XY.
A f
/ /
Mark a dot at the 90°-mark.
f
/
/ /
Remove the protractor and join the B C D
% dot to point Y. Label the point Z.