The greater the opening angle, the greater the contact surface between the fan and the air, and the greater the fan-out wind. The smaller the opening angle, the smaller the contact surface between the fan and the air, and the smaller the fan-out wind.

Some graphics are interlaced with each other, which increases the difficulty of solving. If you turn around a vertex like a fan, it will often make people feel at a loss and solve the problem quickly.

Behind the fan

Sector is an important figure related to the circle, and it is a part of the circle. Because the circle has the symmetry of axial symmetry, central symmetry and rotation invariance, there is an obvious correspondence in the circle, that is, the central angle of 360 degrees corresponds to the arc length of 360 parts and the sector area of 360 parts, that is, the central angle of 1 degree corresponds to the arc length of 1 degree.

The central angle of 1 degree corresponds to the sector area of 1 degree. If R is taken as the radius, the arc length of a sector with a central angle of n degrees is equal to n/360×2πR, and the area of a sector with a central angle of n degrees is equal to n/ 360×πR2. It can be seen that the sector area is related to the central angle (vertex angle) and the radius of the circle, and there is a certain proportional relationship between the sector area and the area of the circle.