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Balkan MO Shortlist
2014 Balkan MO Shortlist
G2
G2
Part of
2014 Balkan MO Shortlist
Problems
(1)
balkan G-2 2014
Source: Balkan MO G-2
6/10/2015
Triangle
A
B
C
ABC
A
BC
is said to be perpendicular to triangle
D
E
F
DEF
D
EF
if the perpendiculars from
A
A
A
to
E
F
EF
EF
,from
B
B
B
to
F
D
FD
F
D
and from
C
C
C
to
D
E
DE
D
E
are concurrent.Prove that if
A
B
C
ABC
A
BC
is perpendicular to
D
E
F
DEF
D
EF
,then
D
E
F
DEF
D
EF
is perpendicular to
A
B
C
ABC
A
BC
geometry