The calculation formula of arc length is a mathematical formula, L=n× π× r/ 180, L = α× r ... where N is the degree of central angle, R is the radius, and L is the arc length of central angle.

In a circle with radius r, because the arc length subtended by the central angle 360 is equal to the circumference of the circle C=2πr, the arc length subtended by the central angle n is L = n π r ÷ 180 (L = n X2π r/360).

A semicircle is a one-dimensional trajectory of points forming a semicircle. The radian of a semicircle is always 180 (equivalent to π radian or half a circle). ? [1] It has only one symmetry line (reflection symmetry). Two endpoints of any diameter of a circle divide the circle into two arcs, and each arc is called a semicircle. The semicircle should be separated from the semicircle, because the semicircle is just an arc.

It is a half circle, and the center position of the half circle is the center position of its concentric circle. It has only one diameter, but it has countless radii and an axis of symmetry.

Extended data

A semicircle can be used to construct the arithmetic and geometric mean of two lengths using a ruler and compasses. If we make a semicircle with a diameter of a+ b, the length of the radius is the arithmetic average of A and B (because the radius is half the diameter). ?

The geometric mean can be obtained by dividing the diameter into two sections with lengths A and B, and then connecting their same ends into a semicircle with a line segment perpendicular to the diameter. The length of the line segment obtained is a geometric average, which can be proved by Pythagoras theorem. ?

This can be used to realize the orthogonality of the rectangle (because the square whose side length is equal to the geometric average of the side length of the rectangle is the same as the area of the rectangle), so an equirectangular area of the rectangle can be constructed, such as an arbitrary polygon (but not a circle).

Baidu encyclopedia-arc length calculation formula