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Official Ukraine Selection Cycle
Kyiv City MO
Kyiv City MO - geometry
Kyiv City MO Juniors 2003+ geometry
2020.9.41
2020.9.41
Part of
Kyiv City MO Juniors 2003+ geometry
Problems
(1)
angle wanted, cyclic ABCD, AB=BC=CD, AE//CD (2020 Kyiv City MO 9.4.1)
Source:
9/20/2020
The points
A
,
B
,
C
,
D
A, B, C, D
A
,
B
,
C
,
D
are selected on the circle as followed so that
A
B
=
B
C
=
C
D
AB = BC = CD
A
B
=
BC
=
C
D
. Bisectors of
∠
A
B
D
\angle ABD
∠
A
B
D
and
∠
A
C
D
\angle ACD
∠
A
C
D
intersect at point
E
E
E
. Find
∠
A
B
C
\angle ABC
∠
A
BC
, if it is known that
A
E
∥
C
D
AE \parallel CD
A
E
∥
C
D
.
geometry
angles
equal segments