ELI5: Explain Like I'm 5

Casey's theorem

Okay kiddo, so let's talk about Casey's theorem. First things first, do you know what a circle is?

A circle is a shape that is round and has no corners. Now imagine there are four circles of different sizes that are all connected to each other, kind of like four bubbles. This is called a "kissing circles" configuration.

Casey's theorem talks about how to find the radius of a fifth circle that just touches the four other circles in this kissing configuration. The circle we are trying to find is called the "inscribed circle".

To find the radius of this inscribed circle, we need to use some math. We need to know the size of the four other circles, which we call A, B, C, and D. We also need to know the distances between the centers of each of these circles.

Once we have all of this information, we can use a formula to calculate the radius of the inscribed circle. It might sound complicated, but it's kind of like a puzzle that we have to put together using the information we have.

So that's Casey's theorem in a nutshell, kiddo. It's a way to find the radius of a fifth circle that touches four other circles in a kissing configuration using some math and a formula. Pretty cool, huh?