Lemme du demi-parallélogramme :
aire(ABD)= aire(BCD)

Lemme du trapèze :
aire(EFG)= aire(EFH)

A = (-2.4, -0.72)
B = (3.46, -0.76)
a = Segment(A, B)
C = (5.46, 2.68)
b = Segment(B, C)
c = Line(C, a)
d = Line(A, b)
D = Intersect(d, c)
e = Segment(A, D)
f = Segment(D, C)
g = Segment(D, B)
poly1, b_1, a_1, d_1 = Polygon(A, D, B)
poly2, d_2, b_2, c_1 = Polygon(B, C, D)
h = Line(A, B)
i = Line(D, C)
E = Point(h)
F = Point(h)
G = Point(i)
H = Point(i)
poly3, f_1, e_1, g_1 = Polygon(E, G, F)
poly4, f_2, e_2, h_1 = Polygon(E, H, F)
j = Segment(G, H)