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Geometry & MeasuresLow Exam FrequencyAQAEdexcelOCRWJEC

Cosine Rule

Revise Cosine Rule in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears less often, but it can still pick up marks when it appears in mixed-topic papers.

Study this topic

1

When Sine Rule Fails

Introduction2

The Cosine Rule

Key Facts3

Method

Deep Dive4

Worked Example: Finding a Side

Notes

Sample Flashcards

Cosine Rule
a² = b² + c² - 2bc cosA. Use for SAS or SSS. Like Pythagoras with a twist!
Cosine Rule
a² = b² + c² - 2bc cos A

Sample Questions

Which formula is the cosine rule for finding side a?

  • A. a² = b² + c² − 2bc cosA
  • B. a/sinA = b/sinB
  • C. a² = b² + c²
  • D. cosA = (b + c − a) / 2bc
1 markfoundation

Show that when angle A = 90°, the cosine rule reduces to Pythagoras' theorem.

2 marksstandard

12

exam-style questions

3

revision flashcards

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