In this activity, we will solve problems by calculating missing angles on parallel lines.
There are three rules.
1 Alternate angles
Alternate angles form a Z shape.
The angles are the same size.
2 Corresponding angles
Corresponding angles form an F shape.
The angles are the same size.
3 Co-Interior angles
Co-interior angles form a C shape - sometimes known as supplementary angles.
They are NOT the same, but they add up to 180o
Make a note of the three rules and we will look at the way they are used in a question.
Example
Find the missing angles and give reasons.
Answer
Angle A forms a Z shape with 58o
A = 58o (alternate angles)
Angle B forms a C shape with 110o
B = 180 - 110 = 70o (co-interior angles)
Angle C is an X from 110o
C = 110o (vertically opposite)
When we get questions like this in an exam, there are as many marks for the reasons as there are for the answer!
Let's try some questions!