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This topic covers the sine rule and cosine rule for finding missing sides and angles in non-right-angled triangles, and the area formula ½ab sin C. It's a core topic in GCSE and iGCSE Maths with Edexcel and the other major boards. This free interactive course teaches the method with worked examples and gives instant-feedback practice questions to lock it in.
How you do it
Use the sine rule when you have a matching side and angle pair, and the cosine rule when you have three sides, or two sides and the angle between them. Area is half ab sin C. Watch for the ambiguous case where an obtuse angle also fits.
Before you start
Everything here rests on trigonometry in right-angled triangles. Getting it right here pays off in non-right-angled triangle problems. Higher tier students all cover it.
What you learn
SOH CAH TOA only works in right-angled triangles. For any triangle, two new rules let you find missing sides and angles, and a third gives the area — even without a perpendicular height. The course works through the sine rule, the cosine rule and area of a triangle, and choosing the rule. Every section has instant-feedback practice questions matched to Edexcel iGCSE 4MA1 and the other major GCSE boards, and the course finishes with full exam-style questions you mark yourself.
Related Topics
Sine & Cosine Rule is a Geometry topic in the GCSE syllabus, covered here at Higher tier. The course is built from 3 concept sections, 2 worked examples and 3 check points before the exam-style set. It sits alongside Transformations, Trigonometry, Vectors and Volume & Surface Area in the same strand. For unlimited practice, the Geometry revision engine builds new questions on demand and records your accuracy.
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