What is the projective theorem?

Projection theorem of right triangle (also called Euclid theorem): In a right triangle, the height on the hypotenuse is the proportional average of the projections of two right angles on the hypotenuse. Each right-angled edge is the median of the projection of this right-angled edge on the hypotenuse and the proportion of the hypotenuse. In the formula Rt△ABC, ∠ BAC = 90, and AD is the height on the hypotenuse BC, then the projective theorem is as follows: (1) (ad) 2; =BD DC，(2)(ab)^2； = BD BC, (3) (AC) 2; =CD BC. Equal product formula (4)ABXAC=BCXAD (proof of usable area)

The so-called projection is the orthographic projection. Projection theorem of right triangle (also called Euclid theorem): In a right triangle, the height on the hypotenuse is the proportional average of the projections of two right angles on the hypotenuse. Each right-angled edge is the median of the projection of this right-angled edge on the hypotenuse and the proportion of the hypotenuse. The content of junior high school projective theorem: the content of projective theorem is: in a right triangle, each right-angled side is the median of the projection of this right-angled side on the hypotenuse, and the high line on the hypotenuse is the median of the projection of two right-angled sides on the hypotenuse.