Once you finish a book on geometry, everyone wants help. 🙂
I wound up making this short video on how to find the center of a circle for my dad. It’s not ideal; I need a better set-up for making videos at my desk. But the essence of it are these steps:
- On a given circle, find three points about 1/3 of the way around the circle, A, B, and C.
- Arc the distance AB center A, and BA center B, so the arcs overlap one another at two points, D and E. Draw a line between D and E — the center will be on that line.
- Arc the distance AC center A, and CA center C, so the arcs overlap one another at points F and G. Draw the line between D and E — the center has to be on that line.
- Point O is the place where lines DE and FG cross. That’s the center of the circle.
I hope this helps!