GCSE Maths: Sine & Cosine Rule
Apply the sine rule and cosine rule in non-right-angled triangles. Practise it with adaptive questions for AQA, Edexcel, OCR and Eduqas.
What you need to know
The concepts examiners test on sine & cosine rule, and what each one is really asking.
Where marks get lost
The exam technique that separates a correct method from a correct answer.
- Using SOHCAHTOA on non-right-angled triangles
- Labeling the triangle wrong (side a must be OPPOSITE angle A)
- Forgetting to square root at the end of the Cosine Rule for finding a side
- Calculator error: calculating b²+c² and then subtracting 2bc before multiplying by cosA (BIDMAS error)
Sine & Cosine Rule questions students ask
Is Sine & Cosine Rule on the Foundation paper?
Yes. Sine & Cosine Rule appears at both Foundation and Higher tier, though Higher papers take it further.
What should I know before starting Sine & Cosine Rule?
It builds on SOHCAHTOA and Solving equations and Calculator skills. If those feel shaky, practise them first — Sine & Cosine Rule questions assume them.
What is the most common mistake in Sine & Cosine Rule?
Using SOHCAHTOA on non-right-angled triangles.
Which exam boards cover Sine & Cosine Rule?
All four we support — AQA, Edexcel, OCR and Eduqas. GCSE Maths subject content is set by the DfE, so the topic is common to every board; what changes is the paper structure and the grade boundaries.