Faire varier le curseur a et observer 
la position du point F 

A = (3, 0, 0)
B = (0, 3, -8.881784197001252E-16)
C = (-1, -2, 0)
poly1, c, a_1, b = Polygon(A, B, C)
D = (0, 0, 3)
d, faceABD, faceBCD, faceACD, arêteAD, arêteBD, arêteCD = Pyramid(poly1, D)
a = 4 (slider from -10 to 10, step 0.1)
e = Line(B, C)
h = Line(A, B)
i = Line(A, C)
E: A + (3 / 4 * Vector[A, B]) + (1 / 4 * Vector[A, C])
F: A + ((a - 1) / a * Vector[A, B]) + (1 / a * Vector[A, C])
M: A + ((a - 1) / a * Vector[A, B])
N: A + (1 / a * Vector[A, C])
f = Segment(F, M)
g = Segment(F, N)