Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

4 Molesworth’s pocket-book Tkigonometbical Surveying. 1.—Given the line B and the angles c and a, to find A. Find the angle b — 180° — (c 4- a), then sin. a A = B -—-; sin. (180° — a) , A = B--------—------, if the angle a be greater sin. b than 90°. 2 .—Given the lines A, B, and an opposite angle a, to find the angle b. Sin. b = B • 3 .—Given the lines B and C, and the included angle a, to find the side A ; A = B2 + C2 — 2 B C cos. a. Curvature and Refraction. D = distance in statute miles. C — curvature in feet = f D2 approximately. C — R = curvature less refraction = | D2 ap- proximately. C-R. 11 -66 2 I 2-67 31 6 4 \ 10'67 5 16-6” C —B. 1 jü. C. I C — B. 'I D. I C. ■57 6 24 20’57 12 96 2’29 7 32’67 28 • 00 14 130 5’1 + 8 42’67 36'5? 16 170 9-14 9 54 46-30 18 216 14-29 10 66'67 57'51 20 266-7 I IV uO U » Il I 82 112 146 185 228-6