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Saint Petersburg Mathematical Olympiad
2022 Saint Petersburg Mathematical Olympiad
3
Isogonal lines wrt angle BIC
Isogonal lines wrt angle BIC
Source: St Petersburg 2022 10.3
September 28, 2022
geometry
Problem Statement
Given is a triangle
A
B
C
ABC
A
BC
with altitude
A
H
AH
A
H
, diameter of the circumcircle
A
D
AD
A
D
and incenter
I
I
I
. Prove that
∠
B
I
H
=
∠
D
I
C
\angle BIH = \angle DIC
∠
B
I
H
=
∠
D
I
C
.
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