Trigonometry rewards precision, and that’s exactly where students trip up. Below are the recurring Trigonometry mistakes that pull grades down on Cambridge 0580 — with why they happen and how to avoid each one.
1. Using the wrong trigonometric ratio. Students confuse which sides are opposite, adjacent, and hypotenuse relative to the angle being used, leading them to select sin instead of cos or tan. For example, for a right-angled triangle with angle 40 degrees, hypotenuse 10 cm, student uses sin 40 = adj/10 instead of cos 40 = adj/10.
2. Forgetting to check calculator mode (degrees vs radians). Scientific calculators can be set to radians or degrees. Students often do not check, especially after using the calculator for other subjects. For example, sin 30 in radian mode gives 0.988 instead of the correct 0.5 in degree mode.
3. Incorrect bearing notation. Bearings must be measured clockwise from North and written as three figures, but students sometimes measure anticlockwise or from other directions. For example, writing a bearing as 45 degrees instead of 045 degrees, or measuring from East instead of North.
The Bigger Picture
Trigonometry errors are largely preventable with careful diagram labelling and systematic checking. Always draw a clear diagram, label all known sides and angles, and decide which rule or ratio to use before picking up your calculator. Check your calculator is in degree mode at the start of every exam. For bearings, always draw a North line at every point and measure clockwise. Show all working clearly as method marks are available even if your final answer is incorrect.
These three are the worst offenders, but they aren’t the whole list. For the full set of trigonometry mistakes — with more worked examples — see our Trigonometry common mistakes resource, or work through the Trigonometry topic hub.
One Question Students Always Ask
What are the most common trigonometry mistakes in IGCSE exams?
The most common trigonometry mistakes include using the wrong trigonometric ratio and forgetting to check calculator mode (degrees vs radians). These errors account for a significant proportion of lost marks. Understanding why they happen and practising the correct methods will help you avoid them.
Want feedback on exactly where you’re losing trigonometry marks? Teacher Rig’s one-to-one online sessions diagnose and fix these errors fast. Book a trial class.
Need Help With IGCSE Maths?
Book a 60-minute trial class with Teacher Rig and get personalised guidance for your IGCSE Maths preparation.