The first six books of the elements of Euclid : with a commentary and geometrical exercises ; to which are annexed a treatise on solid geometry, and short essays on ancient geometrical analysis, and the theory of transversals (1861)
Lardner, Dionysius, 1793-1859 · London : Print. for Taylor and Walton · leaf 289
producing it on both sides of theplane of the square. From the points ABCDinflect on this perpendicular, at both sides ofthe planes, lines equal to the side of the square.It is evident that those which are on the sameside of the plane will meet the perpendicular atthe same point. Let these points… … BOOK THE THIRD. 271 These two pyramids united form a regular solid with eight trian-gular sides, and of which the square is a diagonal plane.This solid is therefore the regular octacdron. (155) Cor. 1. — The inclinations of the planes of every pair ofadjacent faces are equal. From D and B draw…
Geometry
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