The red scarf has three angles, including two acute angles and an obtuse angle. In our mathematical geometry, there are acute angles, right angles, obtuse angles, flat angles, rounded corners, negative angles, positive angles and bad angles. These angles have nothing to do with the length of the side, but with the radian of the angle, that is, the degree of the angle. The greater the radian of an angle, the greater the angle, the smaller the radian and the smaller the angle.
1, acute angle
An acute angle is the radian of an angle, greater than 0 degrees, and an angle less than 90 degrees is an acute angle. Of the three corners of a red scarf, the smallest two are acute. When we compare "yes" with our forefinger and middle finger, the gesture we draw is an acute angle.
2. Right angle
A right angle is an angle whose radian is equal to 90 degrees. When we transform a square into a rectangle, we see that the four corners of the rectangle and the square are right angles, and the two sides of the right angle are vertical.
3, obtuse angle
An obtuse angle is an angle whose radian is greater than 90 degrees and less than 180 degrees. The common obtuse angle in our life is to open the fan, and the angle is the obtuse angle.