Finding the Centre & Radius (Edexcel AS Maths): Revision Note
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Finding the Centre & Radius
How can I find the centre and radius from any form of the equation of a circle?
A circle equation in a different form can always be rearranged into (x- a)2 + (y - b)2 = r2 form in order to find the centre and radius
This will often involve completing the square
![Circle Ctr Rad Illustr 1, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/3.2.2-Circle-Ctr-Rad-Illustr-1.png)
Examiner Tips and Tricks
Make sure you are able to rearrange circle equations given in the general form
![Circle Ctr Rad general illustr, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/3.2.2-Circle-Ctr-Rad-general-illustr.png)
Worked Example
![Circle Ctr Rad Example, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/3.2.2-Circle-Ctr-Rad-Example.png)
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