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Taiwan APMO Prelininary
2018 Taiwan APMO Preliminary
1
Trapezoid, DF//BC
Trapezoid, DF//BC
Source: 2018 Taiwan APMO preliminary
November 10, 2020
geometry
Problem Statement
Let trapezoid
A
B
C
D
ABCD
A
BC
D
inscribed in a circle
O
O
O
,
A
B
∣
∣
C
D
AB||CD
A
B
∣∣
C
D
. Tangent at
D
D
D
wrt
O
O
O
intersects line
A
C
AC
A
C
at
F
F
F
,
D
F
∣
∣
B
C
DF||BC
D
F
∣∣
BC
. If
C
A
=
5
,
B
C
=
4
CA=5, BC=4
C
A
=
5
,
BC
=
4
, then find
A
F
AF
A
F
.
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