Trigonometry: SOHCAHTOA

This lesson introduces right-angled triangle trigonometry for AQA GCSE Mathematics. You will learn how to label the sides of a right-angled triangle relative to a given angle, use the sine, cosine and tangent ratios to find missing sides and angles, and apply trigonometry in real-world problems. Trigonometry is a core Higher-tier topic but also appears on Foundation tier.

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Labelling the Sides

Before using trigonometry, you must label the three sides of a right-angled triangle relative to the angle you are working with (call it angle theta).

Side	Abbreviation	Position
Hypotenuse	Hyp	The longest side, opposite the right angle
Opposite	Opp	The side opposite the angle theta
Adjacent	Adj	The side next to the angle theta (not the hypotenuse)

graph TD
    A[Choose angle theta] --> B[Hypotenuse: opposite the right angle]
    A --> C[Opposite: opposite angle theta]
    A --> D[Adjacent: next to angle theta, not hypotenuse]