Mathematics A-Level
cosine rule
What cosine rule means in Mathematics A-Level, as defined for WJEC.
Definition of cosine rule
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Reference: WJEC
States a² = b² + c² − 2bc cos A, used to find a third side given two sides and the included angle, or rearranged to find an angle given all three sides.
Topics that use cosine rule
- Trigonometry (AS Unit 1: Pure Mathematics A) (WJEC A-Level)
Related terms
- area of a triangle
- CAST diagram
- equation solving
- factorisation
- multiple-angle equations
- periodic solutions
- principal value
- trigonometric definitions
Using cosine rule in the exam
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