Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 157
es without the sphere ; and as the same can beshown for every other point of the plane FAG, this plane canhave no point but A common to it and the surface of thesphere ; hence it is a tangent plane (Def. 31). Sch. In the same way it may be shown, that two sphereshave but one point in common, and… … THEOREM XXII. If a regular semi-polygon he revolved about a line passingthough the centre and the vertices of two opposite angles, thesurface described by its perimeter will be equal to tlie axis -multiplied by Uie circumference of the inscribed cvrclr.. BOOK VI. 157 Of ihe Sphere
Geometry · Plane trigonometry
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