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Included angle and opposite side

Included angle and opposite side

Triangle labeled A, B and C with sides a, b and c, angle C highlighted as the included angle and side c shown opposite

The Cosine Rule works in any triangle, not only right-angled triangles. It is most useful when you know two sides and the included angle, or all three sides and want an angle.

The Cosine Rule Lesson

  1. IGCSE
  2. /Maths
  3. /The Cosine Rule

Step-by-step lessons covering Edexcel IGCSE Maths The Cosine Rule for IGCSE Maths. Each lesson works through exam-style questions in Paper 1 and Paper 2 format. Build confidence with the shared Foundation-tier content first, since roughly 40% of Higher-tier marks are targeted at the grades 4–5 boundary that both tiers have in common.

Lessons

SurdsBoundsDirect and Inverse ProportionQuadratic FormulaFactorising Harder QuadraticsAlgebraic FractionsRearranging Harder FormulaeFinding the Area of Any TriangleThe Sine RuleThe Cosine Rule3d Pythagoras and TrigonometryThe Magnitude of a VectorHistogramsConditional Probability