Japanese theorem for cyclic polygons

You know how sometimes you draw a shape like a square or a triangle, right? And you know how you can put little dots at the corners of that shape to help you remember where the corners are?

Well, sometimes you make a shape like that but all of the corners are on a circle. That's called a "cyclic polygon."

Now, the Japanese theorem says that if you draw lines through opposite corners of a cyclic polygon and then draw a line down the middle of each of those lines, those lines will all meet in the same spot!

It's kind of like if you and some friends all draw lines on a piece of paper and then put that paper over a light and shine the light through it. The lines will all meet in the same spot where the light is coming from.

So the Japanese theorem is just saying that if you draw lines in a certain way on a shape where all the corners are on a circle, those lines will all meet in the same spot. Pretty neat, huh?