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Czech-Polish-Slovak Match
2021 Czech-Austrian-Polish-Slovak Match
3
3
Part of
2021 Czech-Austrian-Polish-Slovak Match
Problems
(1)
Interlaced polygons
Source: 2021 Czech-Polish-Slovak Match, P3
8/3/2021
For any two convex polygons
P
1
P_1
P
1
and
P
2
P_2
P
2
with mutually distinct vertices, denote by
f
(
P
1
,
P
2
)
f(P_1, P_2)
f
(
P
1
,
P
2
)
the total number of their vertices that lie on a side of the other polygon. For each positive integer
n
≥
4
n \ge 4
n
≥
4
, determine
max
{
f
(
P
1
,
P
2
)
∣
P
1
and
P
2
are convex
n
-gons
}
.
\max \{ f(P_1, P_2) ~ | ~ P_1 ~ \text{and} ~ P_2 ~ \text{are convex} ~ n \text{-gons} \}.
max
{
f
(
P
1
,
P
2
)
∣
P
1
and
P
2
are convex
n
-gons
}
.
(We say that a polygon is convex if all its internal angles are strictly less than
18
0
∘
180^\circ
18
0
∘
.)Josef Tkadlec (Czech Republic)