What is it
Trigonometry uses the ratios sine, cosine and tangent (SOH CAH TOA) to relate the angles and side lengths of right-angled triangles, allowing missing sides or angles to be calculated.
Why it matters
Trigonometry is essential for GCSE geometry and problem-solving questions, and it's the direct foundation for A-Level trigonometric functions, graphs and identities.
Exam tip
Label the triangle's sides (opposite, adjacent, hypotenuse) relative to the angle you're working with before choosing SOH, CAH or TOA — most errors come from mislabelling the sides, not from the formula itself.
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