Page 128 - ICSE Math 5

Letter X is an example of intersecting lines.
Parallel lines are two lines which run at a particular A B
distance from each other and never meet at a point.
In the figure given alongside, AB is parallel to CD, i.e., C D
AB || CD. Railway tracks are an example of parallel lines.

Perpendicular lines are two lines which intersect each
other at a point when a line is drawn completely A
horizontal to the vertically drawn line.
In other words, two lines are said to be perpendicular C O D
if they meet or intersect each other at right angles. We
will learn about right angles and other types of angles in
this chapter. B

In the figure given alongside AB is perpendicular to CD,
i.e., AB CD.
An addition (+) sign is an example of perpendicular lines.

• When we join two points with a straight line using a ruler, we get a line segment. The figure
given below is a line segment AB and is denoted as AB. Its length can be measured using a
ruler as it has a fixed length. A and B are called the two end points of AB.

A B

• A line segment that extends only in one direction is called a ray. It has one end point. Its
other end can be extended indefinitely. The figure given below is a ray AB and is denoted
as AB with A as its end point.

A B

Now let’s learn about angles and their measures.

Angles C

When two rays meet at a common end point, they form Exterior of
the angle
a figure called an angle. The common end point where
Interior of
the two rays meet is called the vertex of the angle, and Vertex the angle
the two rays are called the arms of the angle. Look at Angle
the figure shown alongside. A Arm B

In the given figure, rays AB and AC are the two arms of
the angle CAB or BAC and A is the vertex. The symbol Top Tip
used to denote the word angle is ‘’. We write either The middle letter
CAB or BAC to name the given angle and read it as that we write to name
angle CAB and angle BAC, respectively. the angle is always the
vertex of the angle.

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