KS3 Mathematics

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KS3 Mathematics

• S1 Labelling Lines and Angles

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Lines
In Mathematics, a straight line is defined as
having infinite length and no width.
Is this possible in real life?
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Labelling line segments
When a line has end points we say that it has
finite length.
It is called a line segment.
We usually label the end points with capital
letters.
For example, this line segment
has end points A and B.
We can call this line line segment AB.
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Labelling angles
When two lines meet at a point an angle is formed.
A
B
C
An angle is a measure of the rotation of one of
the line segments relative to the other.
We label points using capital letters.
Sometimes instead an angle is labelled with a
lower case letter.
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Conventions, definitions and derived properties
A convention is an agreed way of describing a
situation.
For example, we use dashes on lines to show that
they are the same length.
A definition is a minimum set of conditions
needed to describe something.
60
For example, an equilateral triangle has three
equal sides and three equal angles.
60
60
A derived property follows from a definition.
For example, the angles in an equilateral
triangle are each 60.