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Portugal MO
2015 Portugal MO
2
2
Part of
2015 Portugal MO
Problems
(1)
angle <ABC wanted if ABC,ACD,BCD are all isosceles with D between A,B
Source: 2015 Portugal p2
10/10/2020
Let
[
A
B
C
]
[ABC]
[
A
BC
]
be a triangle and
D
D
D
a point between
A
A
A
and
B
B
B
. If the triangles
[
A
B
C
]
,
[
A
C
D
]
[ABC], [ACD]
[
A
BC
]
,
[
A
C
D
]
and
[
B
C
D
]
[BCD]
[
BC
D
]
are all isosceles, what are the possible values of
∠
A
B
C
\angle ABC
∠
A
BC
?
geometry
isosceles
angles