Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 134
BOOK VI. L33 Of the Sphere 29. All diameters of a sphere are equal to each other; andeach is double a radius. 30. The axis of a sphere is any line about which it re-volves ; and the points at which the axis meets the surface,ire called the poles. 31. A plane is tangent to a spherewhen it has but… … 32. A zone is a portion of the sur-face of a sphere, included betweentwo parallel planes which form itsbases. Thus, the part of the surfaceincluded between the planes AEand DF is a zone. The bases ofthis zone are the two circles whosediameters are AE and DF.
Geometry · Plane trigonometry
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