Plane trigonometry, and its application to mensuration and land surveying. Accompanied with all the necessary logarithmic and trigonometric tables (1852)
Perkins, George R. (George Roberts), 1812-1876 · New York, D. Appleton · leaf 77
en the perpendicular is not given, it may be found as follows : the angle ACB will be found bv dividing 360° bv the number of sides in the polygon; and the angle BCD, which is one-half of ACB, can be found by dividing 180° by the number of sides. Hence if we denote the number of sides by n, we… … P \ of s x cotan. 180° n a) And, the perimeter being n x s, we shall obtainarea = \ ofp x n x s = J of s* x n x cotan. 180° n (2-) If the side of the polygon is taken as a unit, then s = 1, and 180° area = i of n x cotan. n (3.) If, in formula (3), we take successively n = 3, 4, 5, 6, 7, &c,we…
Plane trigonometry · Surveying
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![An illustration from Divina proportione : opera a tutti glingegni perspicaci e curiosi necessaria oue ciascun studioso di philosophia: prospettiua pictura sculptura: architectura: musica: e altre mathematice: suavissima: sotile: e admirabile doctrina consequira: e delecterassi: co[n] varie questione de secretissima scientia (1509)](https://img.insideoutlibrary.com/img/200/ia-divinaproportion00paci-56-88.webp)
