Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 176
be revolved about tlie line AF as an axis :then will the surface flescribed by its pe-rimeter be equal to AF multiplied by tJîecircumference of the inscribed circle. From E and D, the extremities of one oftlie equal sides, let fall the perpendicularsEH, DI, on the axis AF, and from the cen-tre O… … BOOK VIII. 177 been shown to be equal to DEx circ. NM (Prop. IV. Sch.).But since the triangles EDK, 0\M, are similar (Book l\.Prop. XXL), ED : EK or 111 : : ON : NM, or as circ. ON :circ. NM ; hence ED X circ. NM=:II1 X circ. ON ;and since the same may l)e shown lor each of the other sides,it is…
Trigonometry · Geometry
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