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 258
Now when AD is within the trianajle, BD+CD =BC, and thereforesin. (C+B) : sin. (C-B) tan. | BC: tan. i (BD-CD). And againwhen AD is without the triangle, BD —CD»=BC,and therefore sin.(C+B) : sin. (C-B) :: tan. i(BD+CD): tan. I BC, or because thetangents of any two arches are reciprocally as their…
Euclid's Elements · Geometry · Trigonometry
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