What is the arc length formula and area formula of the sector

1, fan arc length formula: arc length formula l = a times r, a is the radian of the central angle r

2, fan area formula s = 1 divided by 2 times l times r.

3, fan is a basic concept in plane geometry, is a central angle of a circle with its corresponding arc, the two radii surrounded by the figure. In daily life, fan shape can be seen everywhere, such as folding fan, fan shells, fan and other items in the shape of the fan belongs to the fan, the fan is also widely used in architectural design, mechanical engineering, electronic engineering and other fields, in the design and manufacture of wind turbines and other equipment plays an important role, the fan is not only in mathematics and physics has an important position in traditional Chinese culture also has a deep symbolic significance, the fan in ancient times often be Used as a symbol of identity and culture, the feather fan in the hands of Zhuge Liang represents wisdom and strategy, while the fan in the hands of the ancient talent symbolizes elegance and charm.