Compass alone

That is to make geometric constructions using only the compass.
The problem becomes much mor difficult than with usual compass and straightedge. Of course only points (and circles) can be constructed, and no staright line segment, but it could be proved ainsi que des points et aucun segment de droite, mais on peut montrer (théorème de (Mohr-Mascheroni theorem) taht every point constructible with compass and straightedge can be constructed with compas only. Constructions are often very acrobatic.

Midpoint of segment AB

Given only points A and B, line AB not drawn.
Solution    Construction

Vertices of a square with side AB

Given only points A and B.
Solution    Construction

Centter of a given circle

This is the "Napoleon problem". Given a circle without knowing its center, construct the center.
Solution    Construction

 

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