There are 10 angles in mathematics, namely: acute angle, right angle, obtuse angle, flat angle, rounded corner, negative angle, positive angle, upper angle, lower angle and zero angle.
1, acute angle: refers to an angle (right angle) greater than 0 and less than 90, and acute angle is a bad angle. The sum of the two acute angles is not necessarily greater than the right angle, but it must be less than the right angle.
2. Right angle: When the adjacent angles formed by a straight line and another horizontal straight line are equal, each of these angles is called a right angle, and this straight line is called perpendicular to another straight line.
3. Oblique angle: When the included angle between two straight lines is more than 90 degrees and less than 180 degrees, it is called obtuse angle. Oblique angle is a bad angle.
4. Straight angle: the light rotates around its endpoint. When the starting edge and the ending edge are on the same straight line and in opposite directions, the angle formed is called a straight angle.
5. Fillet: the angle formed by the light rotating around its endpoint. Fillet is equal to 360, which is the angle formed when one side of the angle rotates around the vertex and coincides with the other side.
6. Negative angle and positive angle: when the terminal edge of the angle in the plane rotates around the vertex of the angle, it can have two different directions, one is counterclockwise and the other is clockwise, and the angle generated by counterclockwise rotation is defined as positive angle; The angle generated by clockwise rotation is defined as negative angle.
7. Optimal angle: also known as concave angle, refers to an angle larger than right angle (180) but smaller than rounded corner (360). Right angle, acute angle and obtuse angle are collectively called lower angle.
8. Lower angle: also known as convex angle, refers to an angle greater than 0 and less than180. Right angle, acute angle and obtuse angle are collectively called lower angle. An angle larger than a straight angle 180 and smaller than a rounded corner (360) is called a superior angle (also called a concave angle).
9. Zero degree angle: the angle formed by light without rotation. The starting edge and the ending edge of the zero-degree angle coincide, but the angles at which the starting edge and the ending edge overlap are not all zero-degree angles, such as 360 degrees (2π radians) and -360 degrees (-2π radians).
Knowledge point of mathematical angle
1, the concept of angle A figure composed of two rays from a point is called an angle. An angle consists of a vertex and two sides.
2. Classification of angles: angles less than 90 degrees are called acute angles; An angle equal to 90 degrees is called a right angle; An angle greater than 90 degrees and less than 180 degrees is called an obtuse angle; An angle equal to 180 degrees is called a right angle; More than 180 degrees and less than 270 degrees is called the optimal angle (this is a supplementary content); An angle equal to 360 degrees is called a fillet.
3. Consciousness. Divide the circle into 360 parts on average, and the angle of 1 part is called 1 degree, and recorded as 1 degree. 1 degree is usually used as the unit for measuring angles.
4. Know the protractor. The protractor divides the semicircle into 180 parts, and one part represents 1 degree. The protractor has a center point, a zero scale line, an inner scale line and an outer scale line.