The normal elementary geometry : embracing a brief treatise on mensuration and trigonometry : designed for academies, seminaries, high schools, normal schools, and advanced classes in common schools (1884)
Brooks, Edward, 1831-1912 · Philadelphia : Christopher Sower Co. · leaf 143
de of the frus-tum. We will now show that its base AGO is a mean pro-portional between the two bases of the frustum. Draw GHparallel to BC; then the triangles AGHandDEF, being similar to ABC, are similar to each other, and,hence, equiangular; and since AG equals DE, the triangleAGS equals DEF (B.… … BOOK VI. 139 Cor. This proposition is true for the frustum of any pyra-mid. For, since any pyramid is equal to a triangular pyra>mid having an equal base and equal altitude, by cutting, the pyramids with a plane parallel to the base, and re-moving the upper part, it may be shown that the…
Geometry · Plane trigonometry
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