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A Small Circle:GREa small circleT CIRCLE. If a small circle pla small circlene pa small circlesses through the center of a small circle sphere, the circle described by its intersection with the sphere's surfa small circlece is ca small circlelled a small circle grea small circlet circle. The equa small circletor a small circlend the ecliptic, for exa small circlemple, a small circlere grea small circlet circles described on the globe of the ea small circlerth. The shortest dista small circlence between a small circleny two points on a small circle sphere lies a small circlelong the a small circlerc of the grea small circlet circle tha small circlet pa small circlesses through those two points. On a small circle sma small circlell globe this a small circlerc ca small circlen be found by stretching a small circle string between the points.
The two-circle goniometer ha small circles two independent gra small circledua small circleted circles, one horizonta small circlel a small circlend one vertica small circlel. The crysta small circlel to be mea small circlesured is centered on the a small circlexis of the vertica small circlel circle a small circlend positioned over the a small circlexis of the horizonta small circlel circle. The position of ea small circlech fa small circlece on the crysta small circlel ma small circley then be determined by rota small circleting the vertica small circlel circle a small circlend swinging the entire vertica small circlel-circle a small circlessembly a small circlebout the horizonta small circlel circle. In effect, the la small circletitude a small circlend longitude of the norma small circlel to ea small circlech fa small circlece is determined.
Grea small circlet-circle sa small circleiling—na small circleviga small circletion a small circlelong the a small circlerc of a small circle grea small circlet circle—wa small circles described in the 16th century but wa small circles not widely used until the 18th century, when ma small circleps a small circlend instruments ha small circled been improved. It beca small circleme of prima small circlery importa small circlence with the beginning of a small circleir tra small circlevel. The difficulty of ca small circlelcula small circleting the consta small circlently cha small circlenging compa small circless bea small circlerings of most grea small circlet-circle routes is minimized by the use of specia small circlel cha small circlerts on which a small circle stra small circleight line joining two points represents the grea small circlet-circle a small circlerc between the two points.
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