$ o=2\pi\ r $
$r=\frac{100}{\pi}$
$r≈31,83m$

řešení

A = (1.96, -0.3)
b = 3.18 (slider from 3 to 3.5, step 0.01)
e = Circle(A, b)
obvode = Circumference(e)
a = 10 (slider from 8 to 12, step 1)
B = Point(Circle[A, a])
c = Segment(A, B)
d = Circle(B, b)
f = OrthogonalLine(A, c)
g = OrthogonalLine(B, c)
C = Intersect(e, f, 2)
D = Intersect(e, f, 1)
E = Intersect(d, g, 2)
F = Intersect(d, g, 1)
h = Segment(C, E)
i = Segment(D, F)
vzdalenostCE = Distance(C, E)
TextCE: "\overline{" + (Name[C]) + (Name[E]) + "} \, = \, " + vzdalenostCE
G = (-6.275299483871263, -7.4737910131654335)
H = (17.90921420031957, -7.464928041359764)
r = 31.830988618379067
Texte: "\large {délka\ půlkružnice\  " + (Name[e]) + " = " + (LaTeX[obvode / 2]) + "}"
k = Semicircle(D, C)
p = Semicircle(E, F)
j = false