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 82
ngle. Join AE, and produce BA to F; and because BE is equal to EA,the angle EAB ia equal (5. 1.) toEBA;also, because AE is equal to EC, theangle EAC is equal toECA; where-fore the whole angle BAC is equal tothe two angles ABC, ACB. But FAC,the exterior angle of the triangle ABC,is also equal (32.… … 82 ELEMENTS And because the two angles ABC, BAG of the triansrlo ABC aretogether less (17. I.) than two right angles, and li AC is a right angle,ABC must be less than a right angle; and therefore the angle in asegment ABC, greater than a semicircle, is less than a right angle. Also because ABCD is…
Euclid's Elements · Geometry · Trigonometry
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