1. 1
B
A
c D
E F
SPACE AND SHAPE
Points, Lines and Planes
The building blocks for Geometry are points, lines and planes:
POINT
A point has a position, but it has no size. We represent a point with a small dot, e.g.
Point P
LINE
A line has no beginning and no end. Line AB is represented as follows:
RAY
A ray has a beginning point, but it has no end point, for example the rays of the sun.
The following represents ray CD
LINE SEGMENT
A line segment is a “piece” of a line. It has a beginning and an end point. The
following represents line EF:
PLANE
A plane is a flat surface with length and breadth, but NO height. A rectangle is an
example of a plane figure.
Perpendicular and parallel lines
THE BUILDING BLOCKS OF GEOMETRY
2. 2
P C Q
A
R S
Q
P
PERPENDICULAR LINES
If two lines meet at right angles, we say they are perpendicular. We use the symbol
to indicate that two lines are perpendicular to each other, for example
AC PQ
Parallel lines
Parallel lines are always the same distance apart and will never meet. We use the
symbol to indicate that two lines are parallel to each other, for example
PQ RS
On a diagram parallel lines are represented by arrows on the lines:
3. 3
Exercise 1
1.1 Say whether the line segments are perpendicular, parallel or neither.
a)
b)
c) d)
e)
f) The diagram on the right, two lines intersect at point O.
Determine the sum of angles around the point O.
4. 4
Angles.
Vertex- the point where arms of an angle meet. (plural form: vertices)
Arc – part of the circumference of a circle
Rotate – to turn
How do you indicate an angle? You indicate an angle by drawing and arc.
Example
Exercise 2: Measure and classify angles.
2.1 Classify angles
a)
5. 5
b) In grade 6 you learnt that angles are classified into types. Complete the table
below.
2.2 Measure angles and write their sizes in the following table.
6. 6
2.3 Measure the all the numbered angles in the following figure. Some angles can be
measured directly, others not. Your protractor cannot measure reflex angles like
angles 7 and 8. So you will have to make a plan! : - )
2.4 Construct the angles listed below. The vertex for each of your angles is the point
labelled O where the tiny vertical cute the long horizontal one. Your angles must be
measured anticlockwise.
