Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 142
BOOK VI. 14) Of the Cone. of the perimeter of the base by theslant height (Th. vi). Let us now suppose the numberof sides of the polygon to be indefi-nitely increased: the polygon willthen coincide with the base of thecone, the pyramid will become thecone, and the line Sf which meas-ures the slant… … THEOREM IX. The convex surface of the frustum of a cone is equal to halfthe sum of the circumferences of its two bases multiplied by tinslant height. For, if we suppose the frustum ofa right pyramid to be inscribed inthe frustum of a cone, its convexsurface will be equal to half the pro-duct of its…
Geometry · Plane trigonometry
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