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Problems
Contests
National and Regional Contests
Taiwan Contests
Taiwan APMO Prelininary
2021 Taiwan APMO Preliminary First Round
5
5
Part of
2021 Taiwan APMO Preliminary First Round
Problems
(1)
external bisector
Source: 2021 Taiwan APMO Preliminary First Round
11/21/2020
△
A
B
C
\triangle ABC
△
A
BC
,
∠
A
=
2
3
∘
,
∠
B
=
4
6
∘
\angle A=23^{\circ},\angle B=46^{\circ}
∠
A
=
2
3
∘
,
∠
B
=
4
6
∘
. Let
Γ
\Gamma
Γ
be a circle with center
C
C
C
, radius
A
C
AC
A
C
. Let the external angle bisector of
∠
B
\angle B
∠
B
intersects
Γ
\Gamma
Γ
at
M
,
N
M,N
M
,
N
. Find
∠
M
A
N
\angle MAN
∠
M
A
N
.
geometry
angle bisector