Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 295
qual to the side of the polygonmultiplied by the cosine of the angle which is obtained by di-viding ;{t)0^ by twice the number of sides : the radius beingequal to unity. Let ABCDE he any regular poly-gon. Draw the diagunal AC, aiui fromhe centre F draw FG, perpendicularro AB. Draw also AF, FB ; the… … 360° *27L But in the right-angled triangle ABH, we have A1I = AB cos A = AB cos :mo 2n (Trig. Th. I. Cor.) Remark 1.—When the polygon in question is the equilateraltriangle, the diagonal becomes a side, and consequently halfthe diagonal becomes half a side of the triangle. Remark 2.-Th. L Cor.).…
Trigonometry · Geometry
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