a = 5 (slider from -5 to 5)
r = 5.1 (slider from -5 to 10)
A: (a, a)
B: ((-a), a)
carréABCD, f, g, h, i, C, D = Polygon(A, B, 4)
O: (0, 0)
c = Circle(O, r)
s(x) = (abs(x + a) - abs(x - a)) / 2
eq3: (s(x))^(2) + (s(y))^(2) = r^(2)