ELI5: Explain Like I'm 5

Orthocentroidal disk

An orthocentroidal disk is a special shape that can be made by drawing a circle around a triangle and then finding the midpoint of each line in the triangle. These midpoints are then connected to create a smaller triangle within the bigger triangle.

The cool thing about this smaller triangle is that it has some special properties. It passes through the center of the circle (called the circumcenter) and also through a point called the orthocenter. The orthocenter is where the three lines that make up the sides of the triangle intersect if they were extended to go all the way through the triangle.

So, the orthocentroidal disk is just a disk (or circle) that is centered at the circumcenter and goes through the orthocenter. This special shape has some neat mathematical properties that make it useful in geometry and other fields.