A treatise on surveying and navigation: uniting the theoretical, practical, and educational features of these subjects (1857)
Robinson, Horatio N[elson], 1806-1867. [from old catalog] · Cincinnati, J. Ernst; Toledo, Anderson, Burr, & co. · leaf 50
ved in problem 15, book 1). On C=, as radius, describe a quadrant; take AD=45°, AB=60°, and ^£=90°, then £E=30°. Join AB, CB, and draw Bn, perpendicular to CA. Draw Bm,parallel to AC. Make the angle CAff=90°, and draw CDH. In the A ABC, the angle ACB=Q0°by hypothesis; therefore, the sum of theother… … 48 SURVEYING. and the sides opposite to equal angles are equal; that is, AB, thechord of 60°, is equal to CA, the radius. In the A CAH, the angle CAHis a right angle ; and by hypoth-esis, A CH. is half a right angle ; therefore, AHC, is also half a rightangle ; consequently, AH=AC, the tangent of…
Surveying · Navigation
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