How to Master Trigonometry for IGCSE

Trigonometry scares a lot of IGCSE students, but it's one of the most predictable topics once you know the decision process.

Start with SOH-CAH-TOA

For right-angled triangles, label the sides (opposite, adjacent, hypotenuse) and pick the ratio that uses the two you have. Ninety percent of the fear disappears once labelling is automatic.

Know when to use the sine and cosine rules

• Cosine rule: when you have two sides and the angle between them, or all three sides.
• Sine rule: when you have a matching side-and-angle pair.

Watch the classic traps

Check your calculator is in degrees, don't round part-way through, and remember bearings are measured clockwise from north.

Practise the decision, not just the sums

The hard part isn't the arithmetic — it's choosing the right tool. Practise identifying which method a question needs before solving it.