1. The projective theorem is also called Euclid theorem. In a right triangle, the height on the hypotenuse is the median of the projection of two right-angled sides on the hypotenuse, and each right-angled side is the median of the projection of this right-angled side on the hypotenuse and the ratio of the hypotenuse. Projective theorem is an important theorem in mathematical graphic calculation.

2. In Rt△ABC, ∠ ABC = 90, and BD is the height on the hypotenuse AC, then the projective theorem is as follows: BD2 = ad CD, AB2 = AC ad, BC2 = CD AC.

3. It was put forward by Euclid, a famous mathematician in ancient Greece and the author of Elements of Geometry.