A right angle means that when the adjacent angles formed by a straight line and another horizontal straight line are equal to each other, each of these angles is called a right angle, and this straight line is called perpendicular to another straight line. An angle smaller than a right angle is called an acute angle, and an angle larger than a right angle but smaller than a right angle is called an obtuse angle.

In geometry and trigonometry, right angles are also called positive angles, which are 90 degrees. It is relative to a quarter of a circle (that is, a quarter of a circle), and two right angles are equal to a half angle (180). An angle smaller than a right angle is called an acute angle, and an angle larger than a right angle but smaller than a right angle is called an obtuse angle. A right angle is equal to 90 degrees, and the symbol is Rt∞.

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Nature:

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

2. In a right triangle, two acute angles are complementary. As shown in the figure, if ∠ BAC = 90, ∠ B+∠ C = 90.

3. 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.

4. The product of two right angles of a right triangle is equal to the product of hypotenuse and hypotenuse height.