Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 56
THEOREM. The angle formed by two secants, is measured by half the diffe-rence of the arcs included between its sides. Let AB, AC, be tw^o secants : thenwill the angle BAC be measured byhalf the difference of the arcs BECand DF. Draw DE parallel to AC : then willthe arc EC be equal to DF, and… … PROPOSITION XXI. THEOREM. 77/c angle formed by a tangent and a chord, is measured by halfof the arc included between its sides. BOOK III. 57 Let BE be the tangent, and AC the cliord, From A, the point of contact, draw thediameter AD. The angle BAD is a riglitangle (Prop. IX.), and is measm-ed…
Trigonometry · Geometry
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