Vertically Opposite Angles

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A = (-2.14, 3.88)
B = (2.6, 1.26)
C = (-2.1, -1.12)
a_1 = Line(A, B)
b_1 = Line(C, B)
a = Angle(A, B, C)
D = Point(b_1)
E = Point(a_1)
b = Angle(E, B, D)
d = Angle(C, B, E)
c = Angle(D, B, A)
text2: "a = b = " + a
text3: "c = d = " + c
e = true
f = true