Ipotesi\!:\ \overline{AC} \cong \overline{BC}; \ 
\overline{DA} \cong \overline{BE}

Tesi\!:\ \triangle CDE\ è\ isoscele

1\ -\ C\^AB \cong C\^BA\ -\ Angoli\ alla\ base\ 
di\ triangolo\ isoscele

2\ -\ D\^AC \cong E\^BC\ -\ Supplementari\ 
di\ angoli\ congruenti

3\ -\ \triangle ADC \cong BEC\ -\ I\ criterio\!:\ 
\overline{AD} \cong \overline{BE} (Ip.);\
\ \ \ \ \ \ \ \overline{AC} \cong \overline{BC} (Ip.);\ 
D\^AC \cong E\^BC (2)

4\ -\ \overline{DC} \cong \overline{EC}\ -\ 
Per\ (3)\
Q.\ E.\ D.

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A = (0.2, -0.28)
B = (5.22, -0.28)
a = Segment(A, B)
b = LineBisector(A, B)
C = Point(b)
c = Segment(A, C)
d = Segment(B, C)
e = Line(A, B)
D = Point(e)
f = Segment(A, D)
E = Intersect(Circle[B, f], e, 2)
g = Segment(B, E)
h = Segment(D, C)
i = Segment(E, C)
α = Angle(B, A, C)
β = Angle(A, B, C)
γ = Angle(D, A, C)
δ = Angle(E, B, C)
poli1, c_1, a_1, d_1 = Polygon(A, D, C)
poli2, c_2, e_1, b_1 = Polygon(E, B, C)