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2017 MMATHS
4
4
Part of
2017 MMATHS
Problems
(1)
2017 MMATHS Tiebreaker p4 - < B_0A_0C_0 = 90^o iff <BAC = 120^o
Source:
10/8/2023
In a triangle
A
B
C
ABC
A
BC
, let
A
0
A_0
A
0
be the point where the interior angle bisector of angle
A
A
A
meets with side
B
C
BC
BC
. Similarly define
B
0
B_0
B
0
and
C
0
C_0
C
0
. Prove that
∠
B
0
A
0
C
0
=
9
0
o
\angle B_0A_0C_0 = 90^o
∠
B
0
A
0
C
0
=
9
0
o
if and only if
∠
B
A
C
=
12
0
o
\angle BAC = 120^o
∠
B
A
C
=
12
0
o
.
geometry
MMATHS