The length or width of the field and equipment on the track and field field is 1.22 meters, except for the width of the track and field, the hurdle frame (springboard)

The length or width of the field and equipment on the track and field field is 1.22 meters, except for the width of the track and field, the hurdle frame (springboard)

The width of track and field is 1.22 meters except the width of track, hurdle and springboard
If there is another, it is the long jump and triple jump to help track width is 1.22 meters

On the calculation formula of circular arc
The arc chord AC is 7.6m long and the arch Bo is 4.6m high
Find the detailed calculation formula

Given that the arc chord AC length L = 7.6m and the arch Bo height h = 4.6m, calculate the radian, arc length C, center angle A and radius r?
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=4.6/2+7.6^2/(8*4.6)
=3.87M
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((7.6/2)/3.87)
=158.24 degrees
=158.24*PI/180
=761786 radians
C = R * a = 3.87 * 2.761786 = 10.687m

Derivation formula of arc length
If the arc length is C, the center angle is n, and the radius is r, then C = what? N = what? R = what?

NπR 180C 180C
C=------ N=------ R=------
180 πR πN
Note: π = pie 3.1415926
I can't see clearly
(ok I admit that the latter two just changed the first one...)