Constructing With Only Ruler or Only Compass
It is possible (according to the Mohr–Mascheroni theorem) to construct anything with just a compass if it can be constructed with a ruler and compass, provided that the given data and the data to be found consist of discrete points (not lines or circles). It is impossible to take a square root with just a ruler, so some things that cannot be constructed with a ruler can be constructed with a compass; but (by the Poncelet–Steiner theorem) given a single circle and its center, they can be constructed.
Read more about this topic: Compass And Straightedge Constructions
Famous quotes containing the words constructing, ruler and/or compass:
“The very hope of experimental philosophy, its expectation of constructing the sciences into a true philosophy of nature, is based on induction, or, if you please, the a priori presumption, that physical causation is universal; that the constitution of nature is written in its actual manifestations, and needs only to be deciphered by experimental and inductive research; that it is not a latent invisible writing, to be brought out by the magic of mental anticipation or metaphysical mediation.”
—Chauncey Wright (1830–1875)
“Can anything be more ridiculous than that a man should have the right to kill me because he lives on the other side of the water, and because his ruler has a quarrel with mine, though I have none with him?”
—Blaise Pascal (1623–1662)
“Constancy in love is a perpetual inconstancy which fixes our hearts successively to all the qualities of the person loved—sometimes admiring one and sometimes another above all the rest—so that this constancy roves as far as it can, and is no better than inconstancy, confined within the compass of one person.”
—François, Duc De La Rochefoucauld (1613–1680)