Point H is the base of the height drawn from the vertex of the right angle B of triangle ABC

Point H is the base of the height drawn from the vertex of the right angle B of triangle ABC to the hypotenuse AC. Find AB if AH = 10, AC = 40

Each leg of a right-angled triangle represents the geometric mean of the hypotenuse and the projection of the leg onto the hypotenuse, this is expressed by the following formula:
b ^ 2 = c * e,
where b is the leg of a right-angled triangle;
c – hypotenuse of a right-angled triangle;
e – projection of leg b onto the hypotenuse c.
Thus:
AB ^ 2 = AC * AH;
AB ^ 2 = 40 * 10 = 400 (conventional square units);
AB = √400 = 20 (conventional units)
Answer: 20 conventional units