CHAP, v.] EXAMPLES OF IRREGULAR PLOTTING 139 



or M . sin H A C = sin a . cos H A C — cos a . sin H A C 



.-. M = sin a . cot H A C — cos . a 



. _ M + cos a 

 cot . H AC = . 



sin a 



Whence true bearing of A C is found, and from the diff. lat. 

 the distance A C follows, together with all the sides and angles 

 of the triangulation. 



Example VI. — The following sketch of the Anamba Islands 

 (Fig. 29) is an illustration of an astronomical base derived from 

 the diff. lat. between A and B, which are about 60 miles apart 

 and invisible from each other. The angles in the triangles 

 B E C, E C D, D C A are all observed. 



Fig. 29 



m '■■ 



Assuming D C = 10,000 units, calculate in the triangulation 

 the sides C A, C B. 



In A A C B, given C A, C B, and Z A C B, find Z « C A B, 

 C B A, and A B. 



Apply these angles to the observed true bearings of C from 



