Elements of geometry and trigonometry . 168 8. The sphere is a solid terminated by a curved surface, allthe points of which are equally distant from a point within,called the centre. The sphere may be con-ceived to be generated by therevolution of a semicircleDAE about its diameter DE :for the surface described inthis movement, by the curveDAE, will have all its pointsequally distant from its cen-tre C. 9. Whilst the semicircleDAE revolving round its di-ameter DE, describes thesphere ; any circular sector,as DGF orFCH, describes asohd, which is named a spherical sector. 10. The radi
Elements of geometry and trigonometry . 168 8. The sphere is a solid terminated by a curved surface, allthe points of which are equally distant from a point within,called the centre. The sphere may be con-ceived to be generated by therevolution of a semicircleDAE about its diameter DE :for the surface described inthis movement, by the curveDAE, will have all its pointsequally distant from its cen-tre C. 9. Whilst the semicircleDAE revolving round its di-ameter DE, describes thesphere ; any circular sector,as DGF orFCH, describes asohd, which is named a spherical sector. 10. The radius of a sphere is a straight line drawn from thecentre to any point of the surface ; the diameter or axis is aline passing through this centre, and terminated on both sidesby the surface. All the radii of a sphere are equal ; all the diameters areequal, and each double of the radius. 11. It will be shown (Prop. VII.) that every section of thesphere, made by a plane, is a circle : this granted, a gj^eat cir-cle is a section which passes through the ce
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Keywords: ., bo, bookcentury1800, booksubjectgeometry, booksubjecttrigonometry
