Page 122 - MAT KS3 Y8 Cambridge CheckPoint

12 Constructions

You will have already used some of the mathematical instruments Key words
that you need to draw lines, angles and 2D shapes.
Make sure you learn and
Ruler Protractor
understand these key words:
80
70
60 110 100
50 130 120
40 140 80 70 60 50 40 30 20 circumference
30 150 90 100 110 120 130 140 150 160 170 180
20 160
10 170 10 radius, radii
180 0
0
cm 1 2 3 4 5
diameter
arc
You also need to be able to use a pair Pair of compasses sector
of compasses to draw circles and chord
arcs. They are usually made of metal segment
or plastic. They have two arms – one line segment
holds a pencil and the other has a midpoint
sharp point on the end. This is to perpendicular bisector
hold the compass in place when you angle bisector
turn it to draw a circle. SSS (side, side, side)
RHS (right angle, hypotenuse,
Before you start drawing circles, you need to know the names of the
side)
different parts of a circle.
The circumference of a circle is a line made up of points that are
always the same distance from the centre. It is the perimeter of a circle.
The radius of a circle is a line segment that joins the centre circumference
of a circle to any point on the circumference. arc
The diameter of a circle is a line segment that passes
through the centre and joins two points on the
sector
circumference. The diameter is twice the length of the
radius.
diameter
An arc is part of the circumference of a circle.
centre
A sector of a circle is the area enclosed between two radii
(plural of radius) and an arc. chord
radius
A chord is a line segment that joins two points on the
circumference of a circle.
segment
A segment is the area enclosed between a chord and an arc.

In this unit you will learn how to draw accurate circles and arcs. You will also learn how to use a pair of
compasses to make other constructions such as perpendicular bisectors and angle bisectors. At the end
of the unit you will use compasses again, to draw triangles when you are given only certain pieces of
information.

120 12 Constructions