Geometry & MeasuresExam Tips

Common Mistakes

Part of Circle Theorems · GCSE GCSE Mathematics revision

This exam tips covers Common Mistakes within Circle Theorems for GCSE Mathematics. Revise Circle Theorems in Geometry & Measures for GCSE Mathematics with 18 exam-style questions and 5 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 5 of 6 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.

Topic position

Section 5 of 6

Practice

18 questions

Recall

5 flashcards

Common Mistakes

X Angle at circumference = 2× angle at centre Angle at CENTRE = 2× angle at circumference Don't reverse the relationship!

X Adjacent angles in cyclic quad = 180° OPPOSITE angles in cyclic quad = 180° Must be opposite, not adjacent

Keep building this topic

Read this section alongside the surrounding pages in Circle Theorems. That gives you the full topic sequence instead of a single isolated revision point.

Worked Example: Centre and Circumference Knowledge Organiser: Circle Theorems The Geometry of Pizza The Eight Circle Theorems

Practice Questions for Circle Theorems

AB is a diameter of a circle. Point C lies on the circle. What is the size of angle ACB?

A. 45°
B. 60°
C. 90°
D. 180°

1 markfoundation

State the circle theorem used to find angle x in the diagram, and explain why it applies in this situation.

2 marksstandard

Quick Recall Flashcards

Angle in Semicircle

Any angle inscribed in a semicircle (with diameter as base) is always 90°. Always!

Cyclic Quadrilateral

If all 4 vertices lie on a circle, opposite angles sum to 180°. Also works in reverse: if opposite angles sum to 180°, then it's cyclic!

18 questions on Circle Theorems — practise free

Instant marking, adaptive difficulty, and 5 spaced repetition flashcards. Free until your GCSEs.

Try PrepWise Free

Worked Example: Centre and Circumference

Knowledge Organiser: Circle Theorems