A = Point(yAxis)
B = Point(xAxis)
C = Point(yAxis)
D = Point(xAxis)
E = Point(zAxis)
a, faceABCD, faceADE, faceABE, faceBCE, faceCDE, arêteAD, arêteAB, arêteBC, arêteCD, arêteDE, arêteAE, arêteBE, arêteCE = Pyramid(D, A, B, C, E)
f = Segment(D, B)
g = Segment(C, A)
F = Intersect(f, g)
h = Segment(E, F)
G = Midpoint(arêteCD)
i = Segment(E, G)
j = Segment(G, F)
α = Angle(E, G, F)