When a straight line crosses two parallel lines there are more angle factswe can look for and use!
1. Corresponding angles are equal - these are angles in a letter 'F'.
2. Alternate angles are equal - these are angles in a letter 'Z'.
3. Supplementary angles add up to 1800 - these are angles in a letter 'U' or 'C' (when the 'U' and the 'C' are made of three straight sides, of course).
The diagram below might help you to see this more clearly. Click on thepairs of angles you want to see and they will be shown on the diagram:
When you've learnt all the above facts, the difficult thing is spotting them in the first place! You need to try out your knowledge by practising questions and ignoring any lines that are 'in the way'! Geometry problems will now be a doddle!