Quand n devient grand, on peut conjecturer que 

\pi=2

n = 1 (slider from 1 to 100, step 1)
L = Sequence((2 i / n, 0), i, 0, n)
C = Sequence(Semicircle[Element[L, i], Element[L, i + 1]], i, 1, n)
A = (0, 0)
B = (2, 0)
c = Semicircle(A, B)
a = Segment(A, B)
D: (1, 1 / n + 0.1)
T1: "l=" + n + "x\frac{\pi}{" + n + "}=\pi"
E = (0, -0.1)
F = (2, -0.1)
u = Vector(E, F)
v = Vector(F, E)