t = 0.39 (slider from 0 to pi, step 0.01)
A: (t, 0)
B: (t, 1)
f: y = 0
g: y = 1
A' = Rotate(A, (-t), B)
t1 = If(0 ≤ t ≤ pi / 3, Polygon[B, A', 3])
C = Rotate(A', pi / 3, B)
A_1: (pi / 3, 0)
B_1: (pi / 3, 1)
c = If(0 ≤ t ≤ pi / 3, CircleArc[B, A', C])
d = If(0 ≤ t ≤ pi / 3, CircleArc[A', C, B])
e = If(0 ≤ t ≤ pi / 3, CircleArc[C, B, A'])
B'_1 = Rotate(B_1, pi / 3 - t, A_1)
C_1 = Rotate(B'_1, pi / 3, A_1)
t2 = If(pi / 3 ≤ t ≤ (2 * pi / 3), Polygon[A_1, B'_1, 3])
k = If(pi / 3 ≤ t ≤ (2 * pi / 3), CircleArc[C_1, A_1, B'_1])
h = If(pi / 3 ≤ t ≤ (2 * pi / 3), CircleArc[A_1, B'_1, C_1])
p = If(pi / 3 ≤ t ≤ (2 * pi / 3), CircleArc[B'_1, C_1, A_1])
A_2: (t - pi / 3, 0)
B_2: (t - pi / 3, 1)
A'_2 = Rotate(A_2, (2 * pi / 3) - t, B_2)
t3 = If((2 * pi / 3) ≤ t ≤ pi, Polygon[B_2, A'_2, 3])
C_2 = Rotate(B_2, ((-pi)) / 3, A'_2)
q = If((2 * pi / 3) ≤ t ≤ pi, CircleArc[B_2, A'_2, C_2])
r = If((2 * pi / 3) ≤ t ≤ pi, CircleArc[A'_2, C_2, B_2])
s = If((2 * pi / 3) ≤ t ≤ pi, CircleArc[C_2, B_2, A'_2])
D = Centroid(t1)
E = Centroid(t2)
F = Centroid(t3)