# Circle points

This project was thrown together rather quickly to solve a geometrical problem: How can you analytically find the circle which passes through three given points? The construction simply demonstrates that the method works, and it not intended to give any further information to the user.

Finding a circle which passes through $$n$$ points is fairly easy to do: simply define a $$\chi^2$$ and vary the centre and radius of the circle until the $$\chi^2$$ is minimised. I didn’t want to pursue a numerical method because it was to be used in the aDetector project to emulate helix reconstruction, where it could be called hundreds or thousands of times per event. Instead I opted to take triplets of points and estimate the circle properties from the triplets, hence I need a fast algorithm to find the circle that passes through three points.