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National and Regional Contests
Czech Republic Contests
Czech and Slovak Olympiad III A
2024 Czech and Slovak Olympiad III A
2
2
Part of
2024 Czech and Slovak Olympiad III A
Problems
(1)
OA=OB if <PAD = <ADP=< CBP =< PCB =< CPD
Source: 2024 Czech and Slovak Olympiad III A p2
5/18/2024
Let the interior point
P
P
P
of the convex quadrilateral
A
B
C
D
ABCD
A
BC
D
be such that
∣
∠
P
A
D
∣
=
∣
∠
A
D
P
∣
=
∣
∠
C
B
P
∣
=
∣
∠
P
C
B
∣
=
∣
∠
C
P
D
∣
.
|\angle PAD| = |\angle ADP| = |\angle CBP| = |\angle PCB| = |\angle CPD|.
∣∠
P
A
D
∣
=
∣∠
A
D
P
∣
=
∣∠
CBP
∣
=
∣∠
PCB
∣
=
∣∠
CP
D
∣.
Let
O
O
O
be the center of the circumcircle of the triangle
C
P
D
CPD
CP
D
. Prove that
∣
O
A
∣
=
∣
O
B
∣
|OA| = |OB|
∣
O
A
∣
=
∣
OB
∣
.
equal angles
geometry