A treatise on surveying, comprising the theory and the practice ; (1887)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, 1840- [from old catalog] ed · New York, D. Appleton and company · leaf 258
, P. Then set at P, sight to theformer position of the instrument, and turn a number of degreesequal to what the observed angle at A wanted of 90°. The in-strument will then point in the direction of the required per-pendicular P B. 357. To let fall a perpendicular to a line from an… … tan. APC + tan. B P 0 Proof: A 0 = P C . tan. A P 0 ; and C B = P C . tan. B P 0 [Trigo-nometry, Art. 4]. Hence A 0 : 0B :: tan. APC : tan. BPO■; and ■ A C : A C + 0 B :: tan. A P 0 : tan. A P 0 + tan. BPO. Consequently, since AC + CB = AB, AC = AB. - . tan.APC + tan. BPC 358. To let fall a…
Surveying
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