Angles in Parallel Lines (Edexcel GCSE Maths)

Revision Note

Written by: Jamie Wood

Reviewed by: Dan Finlay

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Parallel lines are lines that are always equidistant (the same distance apart)
- No matter how far the lines are extended in either direction, they will never meet
Angles are formed when a straight line cuts through two parallel lines

Look for shapes that look like F, Z, or C
Vertically opposite angles can also be used in problems involving parallel lines
- The below diagram shows how identifying angle x, can lead to knowing information about several other angles
  - The green angle opposite is also x, as it is vertically opposite
  - The orange angle must be 180-x as angles on a straight line sum to 180°
You should also be able to spot corresponding angles, alternate angles, and co-interior angles in this diagram

Do not forget to give reasons for each step of your working in an angles question
- These are often needed to get full marks
- You must use the correct names as listed above
  - Do not use F, Z and C angles otherwise you will lose marks!

Find the size of the angles a and b in the diagram below.

Give a reason for each step in your working.

Vertically opposite angles are equal.
Corresponding angles on parallel lines are equal.

You must write down both of these reasons for full marks.

a = 64° (Vertically opposite angles are equal)
b = 64° (Corresponding angles on parallel lines are equal)

Last updated: 17 October 2024

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