Elements of geometry and trigonometry. Revised and adapted to the course of mathematical instruction in the United States (1856)
Legendre, A. M. (Adrien Marie), 1752-1833, Davies, Charles, 1798-1876 · New York : A.S. Barnes · leaf 296
SECOND METHOD. 38. When the nature of the ground will admit of it-measure a base line AB in the direction of the object D.Then measure with the instrument the angles of elevationat A and B. Then, since the ex-terior angle BBC isequal to the sum ofthe nnglcs A and ADB^ it [v that the an- … gle ADB is equal to the difference of the angles of eleva-tion at A and B. Hence, we can find all the parts of thetriangle ABB. Having found BB^ and knowing the angleDBC^ we can find the altitude DC. This method supposes that the stations A and B are onthe same horizontal plane, and therefore it…
Geometry · Trigonometry
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