The two matches cross and are perpendicular to each other, and the third one passes through the intersection of the first two matches and is perpendicular to the plane formed by the first two matches. In this way, every two matches form four right angles, and a * * * is three combinations (1, 2, 1, 3, 2, 3) and a *** 12 right angle.

1, the sum of squares of two right angles of a right triangle is equal to the square of the hypotenuse. ∠ BAC = 90, then AB? +AC？ =BC？ (Pythagorean theorem)

2. In a right triangle, two acute angles are complementary. If ∠ BAC = 90, ∠ B+∠ C = 90.

Extended data:

A measure of the amount of rotation when either of two intersecting lines overlaps the other. Rotation is on the plane of two straight lines and around the intersection. Angle is the unit of measuring angle, and the symbol is 0. A fillet is divided into 360 equal parts, and each part is defined as 1 degree (1 degree).

In a right triangle, the median line on the hypotenuse is equal to half of the hypotenuse (that is, the outer center of the right triangle is located at the midpoint of the hypotenuse, and the radius of the circumscribed circle R=C/2). This property is called the hypotenuse midline theorem of right triangle.

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