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 182
OF GEOMETRY. BOOK II. ISl … And because BG is perpendicular to the plane through DE, EF, itmust make right angles withevery straight line meetingit in that plane (l. def. 2.Sup.). But the straight linesGH, GK in that plane meetit: Therefore each of theangles BGH,BGK is a rightangle: And because BA isparallel (8. 2. Sup.) to…
Euclid's Elements · Geometry · Trigonometry
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