Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 53
T R V Of the Circle half the aic AF, that is, by half thedifference of CFA and CF. But since the tangent DC and thechord A F are parallel, the arc CF isequal to the arc CA : hence the angleBAF, or its equal BDC, which is meas-/ured by half the difference of CFA andCF, is also measured by half the… … THEOREM XIX The cJiOrd of an arc of sixty degrees is equal to the radius ofthe circle. et AEB be an arc of sixty degreesand AB its chord: then will AB be equalto the radius of the circle. For, draw the radii CB and CA.Then, since the angle ACB is at thecentre, it will be measured by the arcAEB:…
Geometry · Plane trigonometry
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