255. With one compass. Can you construct the 4 vertices of a square using only one compass? You have only a sheet of paper and a compass. Resorting to various tricks, such as folding the paper, is not allowed.
255. To mark the vertices of a square using a single compass, first draw a circle. Then, fixing the compass opening and starting from any arbitrarily chosen point \(A\) on the circumference, mark points \(B, C\), and \(D\). From points \(A\) and \(D\) as centers with the radius \(A C\), describe two arcs intersecting at point \(E\). The distance \(E O\) is equal to the side of the desired square. Therefore, if we make marks \(F\) and \(G\) from \(A\) with the radius \(O E\), then \(A, F, D, G\) will be the desired vertices of the square.