Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In differential geometry, the spherical image of a unit-speed curve is given by taking the curve''s tangent vectors as points, all of which must lie on the unit sphere. Differential geometry is a mathematical discipline that uses the methods of differential and integral calculus, as well as linear and multilinear algebra, to study problems in geometry. The theory of plane and space curves and of surfaces in the three-dimensional Euclidean space formed the basis for its initial development in the eighteenth and nineteenth century.