What are alternate angles?
In GCSE maths, alternate angles are a pair of equal angles which are formed either side of a line when the line cuts across two parallel lines. In the diagram below, the orange angles are equal, and the green angles are equal.
Alternate angles are one of the angle properties of parallel lines you should be able to identify. The others are corresponding angles; which are equal, and allied or co-interior angles; which sum to 180 degrees. These angle properties can be used to help solve problems with missing angles. You can read more about all of these angle properties, and see worked examples, in our revision notes.
You may have also seen alternate angles referred to as “Z-angles”, whilst this can help you identify where alternate angles appear (in a z-shape), this term will not score you marks in an exam.
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