Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 140
the hypothenuses areequal; and in the same way it may be proved that all theedges of the pyramid are equal. The triangles, therefore,,which form the convex surface of the prism, are all equal tnftach other. But the area of either of these triangles, as SAB, is equalto half the product of the base… … THEOREM VII. The convex surface of the frustum of a regular pyramid isequal to half the sum of tl/e perimeters of the upper and lowerbases multwlied by the slant height. 140 GEOMETRY. Of the Cone.
Geometry · Plane trigonometry
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