ELI5: Explain Like I'm 5

Pappus's hexagon theorem

Imagine you have a bee that flies from a flower to another flower and then to another flower and keeps going until it comes back to the first flower. Now, if you draw lines from each flower to the next one in sequence, you'll create a closed shape that looks like a hexagon (a six-sided figure). This shape is called the "bee's path."

Pappus's Hexagon Theorem talks about this hexagon and gives us some really cool information about it. If we draw three lines across the hexagon, one passing through each set of parallel sides, and we label the points where these lines intersect the hexagon, we get six points in total. These points, in groups of three, form three pairs of opposite sides of a triangle.

What's amazing is that if we take these three pairs of opposite sides of the triangle and extend them to meet at three points, those three points will always lie on the same straight line. It doesn't matter how many flowers the bee flies to or how far apart they are - this line will always exist.

Basically, Pappus's Hexagon Theorem shows us that there is an amazing relationship between the hexagon formed by the bee's path and the triangle formed by the lines we drew across it. Even though they seem like completely different shapes, they are connected in a special way that will always result in a straight line.