If the altitude is drawn to the hypotenuse of a right triangle, then…
The two triangles formed are similar to the original (big) triangle and to eachother
In a right triangle, the length of the altitude from the right angle to the big hypotenuse is…
The geometric mean of the lengths of the two segments of the hypotenuse
In a right triangle, the altitude from the right angle to the hypotenuse divides the hypotenuse into two segments
Each leg of the big right triangle is the geometric mean of the whole hypotenuse and the segment of the hypotenuse that’s adjacent to that leg