What is the law of projection?

Theorem: In a right triangle, the height on the hypotenuse is the median term of the ratio of the projection of two right-angled sides on the hypotenuse, and the right-angled side is the median term of the ratio of the projection of this right-angled side on the hypotenuse to the hypotenuse. ? Among them, the vertical foot from a point to a straight line is called the orthogonal projection of the point on this straight line. The line segment between the orthographic projections of two endpoints of a line segment on a straight line is called the orthographic projection of the line segment on the straight line. ?

Projective theorem; ? Let the right triangle ABC, AB be the hypotenuse and CD be the height, then? Ac = the square AC =AD×AB? The square of CB =BD×BA? Square of CD =AD×DB? Equal product formula; ? AD×AC=AB×AC？ Launch; AC/AB=AC/AD (ratio)? As shown in the figure ∠ ACB = 90 and CD⊥AB, then AC 2 = AD× AB, BC 2 = BD× AB and CD 2 = AD× BD. The above proportional expressions are collectively referred to as projective theorems. It is mainly used to solve the problem of connecting the hypotenuse of a right triangle and the fixed point with the hypotenuse, such as giving the length of AD and BD to find AC:BC.