Who can explain the following projective theorem! thank you

In a right triangle, the height on the hypotenuse is the median of the ratio of the projection of two right-angled sides on the hypotenuse, and the right-angled side is the median of the ratio of the projection of this right-angled side on the hypotenuse to the hypotenuse.

The origin of projective theorem! -By the Ice Empire

Projective Theorem: On a cloudless sunny day in Wan Li, a small shadow appears when the sun shines on the bamboo pole, so it is called projective theorem, which is an ancient proof problem with a history of 500 years.