Elements of geometry : containing books I to VI and portions of books XI and XII of Euclid, with exercises and notes (1881)
Smith, J. Hamblin (James Hamblin), 1829-1901, Kirkland, Thomas, 1835-1898 · Toronto : W.J. Gage · leaf 158
, III. 20. and / BOC= twice z BDO, III. 20. .-. sum of z s AOC, £00= twice sum of z s ADO, BDO, that is, z ^0J5=twice z ADB. Q. E. D. Note. In fig. 1, z AOB is drawn a flat angle,and in fig. 2, z AOB is drawn a reflex angle. Def. XII. The angle in a segment is the angle contained bytwo straight… … Let BAC, BDC be angles in the same segment BADC. Then mnst l BAC= a BDC.First, when se<;jmeiit BADC is greater than a semicircle, From 0, the centre, draw OB, <)(\ (Fig. 1.) Then, •. z £OC=twice z BAC, III. 20. and z BOC= twice z BDC, III. 20. ..lBAC= I BDCNext, when segment BADC is less than…
Geometry · Geometry, Plane
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