Cartesian Equation of a Circle | ExamSolutions

In this video I show you how to calculate the cartesian equation of a circle given the centre and radius.

[nidurnevets]

Thanks for the very clear explanation. I am learning/relearning mathematics just for my own benefit, now that I am semi-retired. Thanks again!

[smallestdude]

Thanks for the clear explanation, idk why I'd been overcomplicating this for so long

[lordangel]

u should add this video in your cie Pure 1 playlist on the website when u have the time. I already gave the exam and didnt know the syllabus was updated haha had to skip the circle question in the exam. Cheers. ( On that note, if u can.. update the playlists for all Cie modules on your website if u have the time)

[fatmafaizal]

hello, in the question it showed which points should be taken as the diameter, in my book it doesnt mention that in the question. how do i know what to take as my diameter? Eg: Points R(-2, 1), S(4, 3) and T(10, -5) lie on the circumference of the circle. Find equation of the circle. How do i know which is my diameter?

[stevedl]

I`ve just completed my GCSE in Maths. Something troubles me about Geometry in general. It is this : If there are four points, a b c d that lie on the circumference of a circle, then there must be a fifth point, e, that is equidistant from a b c d. e being the centre of the circle.  But if any of the points a b c d are moved in any straight line, to any degree, then a circle no longer exists, and neither does the centre. This must mean that there can be no centre of anything, surely,  that is not capable of being described in terms of a circle ( or sphere ) ?
But geometric points are infinitely small. So, presumably an infinite number of points can fit within - say a triangle. But if the 3 vertices of the triangle don`t lie on a circumference, then there can be no centre of the triangle - ie none of the infinite number of points within the triangle are enough to locate the centre. Maybe the answer is one of definition, but this seems somehow un-satisfactory. Does it answer why an infinite number of points is not enough to locate a centre of a non-circumscribed triangle ?
Hope this makes sense. I don`t know whether to carry on studying Mathematics or not.