Construction of Regular 257-Gon
Theorem
It is possible to construct a regular polygon with $257$ sides using a compass and straightedge construction.
Proof
257 is a Fermat prime.
From Construction of Regular Prime $p$-Gon Exists iff $p$ is Fermat Prime it is known that this construction is possible.
$\blacksquare$
Historical Note
It was proved by Carl Friedrich Gauss in $1801$ that the construction is possible.
The first actual constructions of a regular $257$-gon were given by Magnus Georg Paucker in $1822$ and Friedrich Julius Richelot in $1832$.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $257$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $257$