. Bulletin of the United States Geological Survey--Geographic Tables and Formulas. s used by the topographer in the fieldand office, and it is believed that their publication will be useful, notonly to the topographic corps, but to others engaged in similar linesof work. The material has been drawn from various sources, someof it having been prepared from time to time by various members ofthe Geological Survey and the remaining portions having been takenprincipally from publications of the U. S. Coast and Geodetic Surveyand the Smithsonian Institution. The compiling was done by Mr. S. S. Ganne
. Bulletin of the United States Geological Survey--Geographic Tables and Formulas. s used by the topographer in the fieldand office, and it is believed that their publication will be useful, notonly to the topographic corps, but to others engaged in similar linesof work. The material has been drawn from various sources, someof it having been prepared from time to time by various members ofthe Geological Survey and the remaining portions having been takenprincipally from publications of the U. S. Coast and Geodetic Surveyand the Smithsonian Institution. The compiling was done by Mr. S. S. Gannett, and the material wasrevised by Mr. E. M. Douglas and Mr. H. L. Baldwin, respectful 1 v, R. U. Goode,Chairman Topographic Charles D. Walcott, Director United States Geological Survey. GEOGRAPHIC TABLES AND FORMULAS. Compiled by S. S. Gannett. RTTLFS FOR SOLUTION OF RIGHT-ANGLED TRIANGLES. The parts of the figures are—H = hy pothenuse,V = perpendicular,B=base,and the six circular functions of the angle oc at the base of the triangle. Secant Cosecant-\. Fig. 1.—Solution of right-angled triangles. Rule I. The product of two opposite parts = 1, .. either is thereciprocal of the other. Example: Tang oc x cot a = 1, tang oc — , ^. Rule II. Each part = adjacent part divided by the following part, . *. each part = the product of the adjacent parts. cos oc I* Example: Sine a = —r—, sine oc — -ff, B = H X cos a. 10 GEOGRAPHIC TABLED AND FORMULAS. BULL. 214. REDUCTION TO CENTER. In fig. 2 let P=place of instrument; C = center of station; Q=measured angle at P between two objects, A and B; y=smg\e at P between C and the left-hand object, B; r=distance CP; C = unknown and required angle at C; D = distance AC; (r and D must be reduced to same unit, usually meters.) G=distance BC; and A=angle at A between P and C; B=angle at B between P and C.
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