A treatise on special or elementary geometry (1877)
Olney, Edward, 1827-1887, Olney, Edward, 1827-1887. Elements of trigonometry, plane and spherical · New York : Sheldon · leaf 163
s Oa\ then isits area equal to i Oa (AB + BC + CD + DE + EF+ PC + GA). Drawing the inscribed circle, the radii Oa, Ob,etc., to the points of tangency, and the radii of thecircumscribed circle OA, OB, etc. {264, 205), thepolygon is divided into as many equal triangles asit has sides. Now, the… … B 3 C Fig. 229. 327, Cor.—The area of any polygon in which a circle can leinscribed is equal to one-half the product of the radius of the in-scribed circle into the perimeter. The student should draw a figure and observe the fact. It is especiallyworthy of note in the case of a triangle. See Fig.…
Geometry · Trigonometry
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