Mohr–Mascheroni theorem

The Mohr–Mascheroni theorem is a result in geometry that states that it is possible to construct any length using only a compass, without the need for a straightedge. This theorem is named after the German mathematician Max Mohr and the Italian mathematician Giovanni Mascheroni, who independently proved this result. The theorem can be surprising because traditional geometric constructions often rely on both a compass and a straightedge.