Mathematics GCSE
cosine rule
What cosine rule means in Mathematics GCSE, as defined for Pearson Edexcel.
Definition of cosine rule
Check what you remember
Read the wording for your board, then hide it and explain cosine rule in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: Pearson Edexcel
Use a² = b² + c² – 2bc cos A when you know two sides and the angle between them, or when you know all three sides.
Topics that use cosine rule
- Geometry and measures - Mensuration and calculation (Pearson Edexcel GCSE)
Related terms
- Arc
- arc length
- area and volume units
- area of a segment
- Chord
- Circumference
- Composite shapes and solids
- Congruence
Using cosine rule in the exam
Check the command word and mark scheme for your exact question. After comparing your explanation with the reference, use the term in an answer on the linked topic. This practice does not predict an exam mark.
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