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Equation of a Circle (Edexcel International A Level Maths): Revision Note

Roger B

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Roger B

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Equation of a Circle

What do I need to know about the equation of a circle?

  • A circle with centre (a, b) and radius r has the equation

 

Eqn of Circle graph illustr, A Level & AS Level Pure Maths Revision Notes

  •  You need to be able to find the centre and radius of a circle from its equation

Eqn of Circle Illustr 1, A Level & AS Level Pure Maths Revision Notes

  •  You need to be able to find the equation of a circle given its centre and radius

Eqn of Circle Illustr 2, A Level & AS Level Pure Maths Revision Notes

Examiner Tips and Tricks

  • Remember that the numbers in the brackets have the opposite signs to the coordinates of the centre. 

    Eqn of Circle sign flip, A Level & AS Level Pure Maths Revision Notes

     

  • Don't forget to take the square root of the right-hand side of the equation when finding the radius.

Worked Example

Eqn of Circle Example, A Level & AS Level Pure Maths Revision Notes

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    Roger B

    Author: Roger B

    Expertise: Maths

    Roger's teaching experience stretches all the way back to 1992, and in that time he has taught students at all levels between Year 7 and university undergraduate. Having conducted and published postgraduate research into the mathematical theory behind quantum computing, he is more than confident in dealing with mathematics at any level the exam boards might throw at you.