Elements of geometry : containing the first six books of Euclid, with a supplement on the quadrature of the circle, and the geometry of solids : to which are added, Elements of plane and spherical geometry (1826)
Playfair, John, 1748-1819, Euclid · Philadelphia : Marot & Walter · leaf 251
-cular toDB, which will therefore be the sine of the hypotenuse BC;and from the point E let there be c drawn in the [)Iane ABD the straightline EF perpendicular to DB, andlet CF be joined: then CF will beat right angles to the plane ABD,because as was shown of EA in thepreceding proposition, it is… … SPHERICAL TRIGONOMETRY. 251 CE is to the radius, as CF to the sine of the angle CEF (1. PJ. Tr.).But, since CE, FE are at right angles to DEB, which is the corumonsection ot the planes CBD, ABD, the angle CEF is equal to the incli-nation of these planes, (4. del. 2. Su[).), that is to the spherical…
Euclid's Elements · Geometry · Trigonometry
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