Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 109
103 GEOMETRY. Area of Circle. equal triangles as the polygon hassides, in each of which the perpen-dicular on the base will be equal toCD. Now, the area of one of them,as A CB, will be equal to half the pro-duct of CD by the base AB; and thesame will be true for each of the othertriangles : hence,… … THEOREM XXVII. Tlie area of a circle is equal to half the product of the radius bythe circumference. Let C be the centre of a circle :then will its area be equal to half theproduct of the radius A C by the cir-cumference ABE. For, inscribe within the circle aregular hexagon, and draw CD…
Geometry · Plane trigonometry
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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-94-179.webp)
