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National and Regional Contests
Cuba Contests
Cuba MO
2012 Cuba MO
6
6
Part of
2012 Cuba MO
Problems
(1)
AD x BC = AB x DC + BD x AN - 2012 Cuba MO 2.6
Source:
9/18/2024
Let
A
B
C
ABC
A
BC
be a right triangle at
A
A
A
, and let
A
D
AD
A
D
be the relative height to the hypotenuse. Let
N
N
N
be the intersection of the bisector of the angle of vertex
C
C
C
with
A
D
AD
A
D
. Prove that
A
D
⋅
B
C
=
A
B
⋅
D
C
+
B
D
⋅
A
N
.
AD \cdot BC = AB \cdot DC + BD \cdot AN.
A
D
⋅
BC
=
A
B
⋅
D
C
+
B
D
⋅
A
N
.
geometry