The formula of projective theorem in high school mathematics

High school mathematics projective theorem formula: CD? = AD DB BC? = BD BAAC？ = AD ABAC BC=AB CD

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The projection theorem of right triangle, also known as Euclid theorem, means that the height on the hypotenuse is the proportional average of the projections of two right angles on the hypotenuse, and each right angle is the proportional average of the projection of this right angle on the hypotenuse and the hypotenuse.

The formula is as follows: in Rt△abC ∠ ACB = 90, and cd is the height on the hypotenuse AB, then the projective theorem is as follows: ①CD? = AD DB② BC? = BD BA③AC？ = ADAB4ACBC = ABCD (equal product formula, available area proof)

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.

Because the projection is to scale the length of the original figure (called the height in the triangle), the width is unchanged, and because the area ratio of the plane polygon = the square ratio of the side length. So it is the ratio of the length of the figure (called the height in the triangle).

Then this ratio should be the cosine of the angle formed by the plane. Make a right triangle in two planes, so that the hypotenuse and right edge are perpendicular to the edge (that is, the intersection of the plane where the original polygon is located and the projection plane).

Then the ratio of the hypotenuse of a triangle to the other right-angled side is the length ratio of its polygon, that is, the area ratio of a plane polygon. This ratio can be calculated by putting it in a plane triangle.

Euclid (Greek: ε υ κ λ ε ι δ η? 325 BC-265 BC), an ancient Greek mathematician, was called "the father of geometry". During the period of Ptolemy I Soter (323 BC-283 BC), he was active in Alexandria.

His most famous book, The Elements of Geometry, is the foundation of European mathematics, which summarizes five postulates of plane geometry and is widely regarded as the most successful textbook in history. Euclid also wrote some works about perspective, conic curve, spherical geometry and number theory.