Ipotesi\!:\ C\^AB \cong C\^BA\
Tesi\!:\ \overline{AC} \cong \overline{BC}

1\ -\ \overline{AD} \cong \overline{BE}\ -\ 
Per\ costruzione

2\ -\ D\^AB \cong E\^BA\ -\ Supplementari\ di\ 
angoli\ congruenti

3\  -\  \triangle DAB \cong EBA\ -\ I\ criterio\!:\ 
\overline{AB}\ comune;\
\ \ \ \ \ \ \ \overline{AD} \cong 
\overline{BE}\ (1); D\^AB \cong E\^BA\ (2) 

4\ -\ \overline{AE} \cong \overline{DB};\ 
D\^BA \cong E\^AB;\ A\^DB \cong C\^EA\ -\ 
Per\ (3)

5\ -\ D\^BC \cong E\^AC\ -\ Per\ (4)\ e\ (Ip.)\ 
sono\ somma\ di\ angoli\ congruenti

6\ -\ \triangle CAE \cong CBD\ -\ II\ criterio\!:\ 
\overline{AE} \cong \overline{DB}\ (4);\
\ \ \ \ \ \ \ A\^EB \cong B\^DA\ (4);\ C\^AE \cong 
C\^BD\ (5)

7\ -\ \overline{CA} \cong \overline{CB}\ -\ 
Per\ (6)\
Q.\ E.\ D.

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A = (2.58, -2.04)
B = (5.98, -2.02)
a = Segment(A, B)
P:(4.96, 3.64)
α = Angle(B, A, P)
b = Line(A, P)
A' = Rotate(A, (-α), B)
α' = Angle(A', B, A)
c = Line(B, A')
C = Intersect(b, c)
d = Segment(A, C)
e = Segment(C, B)
f = Ray(C, A)
g = Ray(C, B)
D = Point(f)
h = Segment(A, D)
k = Circle(B, h)
E = Intersect(k, g, 2)
i = Segment(B, E)
β = Angle(D, A, B)
β' = Angle(A, B, E)
j = Segment(D, B)
l = Segment(E, A)