A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects (1852)
Robinson, Horatio N[elson], 1806-1867. [from old catalog] · Cincinnati, J. Ernst · leaf 52
ved in problem 15, book 1). On 0==, as radius, describe a quadrant; take AD=4b°f AB=60°, and ^=90°, then BE=30°. Join AB, OB, 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 A (75=60°by hypothesis; therefore, the sum of… … 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 CAR, the angle CAR is a right angle; and by hypoth-esis, A CH, is half a right angle ; therefore, AHC, is also half a rightangle; consequently, AB=AC, the tangent of…
Surveying · Navigation
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