Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 35
THEOREM XXII. [f every side of a polygon be produced out, the sum of all the ouiward angles thereby formed, will be equal to four righi angles (jEOMETRY. Of Polygons … Let A, B, C, D, and E, be the outwardangles of a polygon formed by producingall the sides. Then will A 4-B+ C+D + E=four right angles. For, each interior angle, plus its exte-rior angle, as A + a, is equal to two rightangles (Th. ii). But there are as many exterior as interiorangles, and as many of…
Geometry · Plane trigonometry
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