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U. S. COAST AND GEODETIC SURVEY. 



Problem 3. — To project a great circle, the projection of 

 the pole being given: 



In this case the polar distance is ^ and Pp=Pq=^ in 



figure 18. The circle passes through W and E; hence it is 

 sufficient to locate either p^ or q'; WO is parallel to OP, 



Tig. 18.— Projection of a great circle with given pole projection on stereographic projection, 



and in this manner O can be located; with 6^ as center, with 

 OE as radius, the circle can be constructed. 



Problem 4- — ^To find the locus of centers of all great circles 

 passing through a given point: 



