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This topic covers right-angled trigonometry — using sine, cosine and tangent (SOHCAHTOA) to find missing sides and angles — and the exact trig values for key angles. 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
Label the sides opposite, adjacent and hypotenuse relative to the angle, then pick sine, cosine or tangent using SOHCAHTOA. To find a side, multiply or divide. To find an angle, use the inverse function on your calculator.
Before you start
It assumes you can handle Pythagoras and ratio. It then feeds into the sine and cosine rules and A-Level trigonometry. It appears at Foundation and Higher tier.
What you learn
Trigonometry connects the angles of a right-angled triangle to the lengths of its sides. With three ratios — sine, cosine and tangent — you can find a missing side or a missing angle in any right-angled triangle. If you know two sides, you can find the angle. Both sit inside a right-angled triangle, so the same three ratios apply. The course works through labelling sides and the three ratios, finding a missing angle and exact values, elevation and depression. 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
Trigonometry is part of the Geometry strand of our free GCSE maths courses, studied in Foundation tier. You work through 3 concepts and 2 worked examples, testing yourself at 3 points. Related topics students usually take next include Vectors, Volume & Surface Area, Angles, Area & Perimeter and Circle Theorems. The Geometry revision engine gives you as many extra questions as you want, tracked on your skill tree.
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