Elements of geometry and trigonometry. Revised and adapted to the course of mathematical instruction in the United States (1856)
Legendre, A. M. (Adrien Marie), 1752-1833, Davies, Charles, 1798-1876 · New York : A.S. Barnes · leaf 126
e demonstrated, that tJ/e area ofa triangle is equal to its 2><^rimeler multlqAied by ItaJf the radiusof the inscribed circle. For, the triangles AOB,BOC, AGO, which have acommon vertex at 0, havefor their common altitude theradius of the inscribed circle;hence, the sum of these tri-angles… … rRorosiTioN xxxiii. tiieoeem. In every quxtdrilateral inscribed in a circle, tJie rectanyle of thetwo diayoiia/s is equiualent to the sum of the reciawjlcs ofthe oqrposite sides. Let A BCD be a quadrilateral inscribed in a circle, andAC, BD, its diagonals: then we shall have…
Geometry · Trigonometry
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