Somme des angles d'un triangle

A = (1.26, 4.14)
B = (-2.2800000000000002, 1.1400000000000001)
C = (5.04, -0.28)
poly1, c, a, b = Polygon(A, B, C)
α = 0 rad (slider from 0 to 3.141592653589793, step 0.017453292519943295)
D = Midpoint(c)
E = Midpoint(a)
F = Midpoint(b)
poly2, e, b_1, d = Polygon(B, D, E)
poly3, c_1, e_1, f = Polygon(E, F, C)
B' = Rotate(B, -(α), D)
D' = Rotate(D, -(α), D)
E'_1 = Rotate(E, -(α), D)
poly2', e', b', d' = Polygon(B', D', E'_1)
E' = Rotate(E, α, F)
F' = Rotate(F, α, F)
C' = Rotate(C, α, F)
poly3', c', e'_1, f' = Polygon(E', F', C')
poly4, a_1, d_1, e_2, f_1 = Polygon(A, D, E, F)
β = Angle(B, A, C)
γ = Angle(E, B, D)
δ = Angle(F, C, E)
ε = Angle(F', C', E')
ζ = Angle(E'_1, B', D)
g = Line(E'_1, E')