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Romanian Masters of Mathematics Collection
2018 Romanian Master of Mathematics
6
6
Part of
2018 Romanian Master of Mathematics
Problems
(1)
Geometry with fix circle
Source: RMM 2018 Problem 6
2/25/2018
Fix a circle
Γ
\Gamma
Γ
, a line
ℓ
\ell
ℓ
to tangent
Γ
\Gamma
Γ
, and another circle
Ω
\Omega
Ω
disjoint from
ℓ
\ell
ℓ
such that
Γ
\Gamma
Γ
and
Ω
\Omega
Ω
lie on opposite sides of
ℓ
\ell
ℓ
. The tangents to
Γ
\Gamma
Γ
from a variable point
X
X
X
on
Ω
\Omega
Ω
meet
ℓ
\ell
ℓ
at
Y
Y
Y
and
Z
Z
Z
. Prove that, as
X
X
X
varies over
Ω
\Omega
Ω
, the circumcircle of
X
Y
Z
XYZ
X
Y
Z
is tangent to two fixed circles.
geometry
RMM 2018