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 299
axis. Let PB be the hypotenuse, and P A the fixed axis. Theside A B moving in a plane at right angles to P Adescribes in. that plane a circle B M N. This circleis called the base of the cone. A convex surface,called a conical surface, is described by the motionof the hypotenuse; and as this line,… … BOOK THE FOURTH. 281 The point P is called the vertex, and every right line drawnfrom that point to the circumference of the base is called a sideof the cone. (204) Def. — The line P A is called the axis of the cone. (205) Cor. 1. —It is evident, therefore, that if any plane passthrough the vertex…
Geometry
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