Circles, Arcs And Sectors
Overview
Circles are everywhere, from wheels and clocks to plates and coins, and the same two numbers describe all of them: the distance around the edge and the space inside. Both depend only on the radius and on the famous constant pi. Once you can find the circumference and area of a full circle, a slice of it, a sector or an arc, is just a fraction of the whole.
In this lesson you will use the circumference and area formulas, then extend them to arcs and sectors using the angle at the centre. The biggest pitfall is mixing up the radius and the diameter, since the diameter is twice the radius and using the wrong one doubles or halves your answer. This lesson makes the radius habit second nature.
Objectives
- Carry out calculations involving the circumference and area of a circle.
- Carry out calculations involving arc length and sector area as fractions of the circumference and area of a circle, where the sector angle is a factor of 360°.
- Carry out calculations involving arc length and sector area as fractions of the circumference and area of a circle. (Extended only)
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Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Circles, Arcs And Sectors. 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.
- A circle has radius 7 cm. Using pi = 3.142, what is its circumference to 2 d.p.? A. 21.99 cm B. 43.99 cm C. 153.94 cm D. 307.88 cm Answer: B
- A circle has radius 7 cm. Using pi = 3.142, what is its area to 2 d.p.? A. 21.99 cm^2 B. 43.98 cm^2 C. 153.96 cm^2 D. 615.75 cm^2 Answer: C
- A circle has diameter 14 cm. What is its radius? A. 3.5 cm B. 7 cm C. 14 cm D. 28 cm Answer: B
- A sector of a circle of radius 7 cm has centre angle 90 degrees. What is its area to 2 d.p.? (pi = 3.142) A. 11.00 cm^2 B. 38.49 cm^2 C. 76.97 cm^2 D. 153.94 cm^2 Answer: B
- A sector of a circle of radius 7 cm has centre angle 90 degrees. What is its arc length to 2 d.p.? (pi = 3.142) A. 5.50 cm B. 11.00 cm C. 21.99 cm D. 43.98 cm Answer: B
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