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Problems
Contests
International Contests
Baltic Way
1996 Baltic Way
5
5
Part of
1996 Baltic Way
Problems
(1)
Japanese-Inspired Baltic Way problem
Source: Baltic Way 1996 Q5
3/19/2011
Let
A
B
C
D
ABCD
A
BC
D
be a cyclic convex quadrilateral and let
r
a
,
r
b
,
r
c
,
r
d
r_a,r_b,r_c,r_d
r
a
,
r
b
,
r
c
,
r
d
be the radii of the circles inscribed in the triangles
B
C
D
,
A
C
D
,
A
B
D
,
A
B
C
BCD, ACD, ABD, ABC
BC
D
,
A
C
D
,
A
B
D
,
A
BC
, respectively. Prove that
r
a
+
r
c
=
r
b
+
r
d
r_a+r_c=r_b+r_d
r
a
+
r
c
=
r
b
+
r
d
.
geometry
incenter
rectangle
Euler
geometry proposed