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 30
D; therefore the angle BCDis greater than the angle ADC ;and because the angle BCD of the triangle DCB is greater than itsangle BDC, and that the greater (19. 1.) side is opposite to thegreater angle : therefore the side DB is greater than the si<ie BC; butDB is equal to BA and AC together ;… … ELEMENTS PROP. XXI. THEOR. If from the ends of one side of a triangle, there bedrawn two straight lines to a point within the triangle,these two lines shall be less than the other two sides ofthe triangle, but shall contain a greater angle. Let the two sfrai^lt lines BD, CD be drawn from B, C, the…
Euclid's Elements · Geometry · Trigonometry
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