G'

B: (-1.94797, -4.26601, 0)
C: (5.96605, -4.6935, 0)
D = Point(Circle[Midpoint[B, C], (Distance[B, C] * sqrt(3) / 2), Segment[B, C]])
a, A, faceABC, faceACD, faceABD, faceBCD, arêteAC, arêteAB, arêteBC, arêteAD, arêteCD, arêteBD = Tetrahedron(B, C, D)
I = Midpoint(arêteAB)
J = Midpoint(arêteBC)
K = Midpoint(arêteCD)
L = Midpoint(arêteAD)
M = Midpoint(arêteBD)
N = Midpoint(arêteAC)
f = Segment(I, K)
g = Segment(D, I)
u: (2 / 3 * Vector[D, I])
D' = Translate(D, u)
h = Segment(A, D')