Circle Theorems And Constructions
Overview
A circle looks simple, but the angles hiding inside it obey a tight web of rules: an angle at the centre is always exactly twice its counterpart on the circumference, opposite corners of a cyclic quadrilateral are always supplementary, and a tangent meets its radius at a perfect right angle every time. This topic gives you the full set of Edexcel circle theorems, proved rather than just stated, plus the loci and constructions that turn these ideas into precise ruler-and-compasses drawings.
You will learn to identify which theorem a diagram is asking for, chase an angle through several steps of reasoning, and construct an angle bisector and a perpendicular bisector using nothing but a straight edge and compasses. Circle theorem questions reward students who can name the exact property they used, so this note treats every reason as seriously as the number attached to it.
Objectives
- Understand and use chord, angle and tangent properties of circles
- Know and use properties of a cyclic quadrilateral, including intersecting chord properties and the alternate segment theorem
- Understand and use loci in two dimensions
- Construct bisector of an angle and perpendicular bisector of a straight line using ruler and compasses
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Circle Theorems And Constructions. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- O is the centre of a circle. Points A and B lie on the circumference. The angle at the centre, angle AOB, is 94 degrees. What is the angle at the circumference, angle ACB, for a point C on the major arc? A) 47 degrees B) 94 degrees C) 188 degrees D) 43 degrees Answer: A
- ABCD is a cyclic quadrilateral with angle B = 78 degrees. What is angle D? A) 78 degrees B) 90 degrees C) 102 degrees D) 180 degrees Answer: C
- TA is a tangent to a circle at point A, and O is the centre. What is the size of angle OAT? A) 45 degrees B) 60 degrees C) 90 degrees D) It depends on the radius Answer: C
- Chords PQ and RS intersect inside a circle at point X, with PX = 4 cm, XQ = 9 cm and RX = 6 cm. What is XS? A) 5 cm B) 6 cm C) 7.5 cm D) 13.5 cm Answer: B
- Which locus describes the set of points equidistant from two fixed points P and Q? A) A circle centred at the midpoint of PQ B) The perpendicular bisector of PQ C) A line parallel to PQ D) The angle bisector at P Answer: B
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
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