GCSE · Trigonometry (sine & cosine rules)

The cosine ruleExam-style questions

Why a² = b² + c² − 2bc cos A is Pythagoras with a correction term, when to choose it over the sine rule, and the rearrangement that finds an angle from three sides.

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19 questions · GCSE (Higher) level · mark scheme and worked solution on each · no sign-up to try

DifficultyAll Level 3 Level 4 Level 5

1
In triangle $ABC$ , $b = 9$ cm, $c = 13$ cm and angle $A = 67°$ .Diagram NOT accurately drawn

Work out the length of $a$ . Give your answer correct to 1 decimal place.
Level 3 · 3 marksTry it
2
In triangle $ABC$ , $b = 8.2$ cm, $c = 6.5$ cm and angle $A = 54°$ .

Work out the length of $a$ . Give your answer correct to 3 significant figures.
Level 3 · 3 marksTry it