Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In differential geometry, the tangent indicatrix of a closed space curve is a curve on the unit sphere intimately related to the curvature of the original curvee. In mathematics, a curve is, generally speaking, an object similar to a straight line but which is not required to be straight. Often curves in two-dimensional (plane curves) or three-dimensional (space curves) Euclidean space are of interest. Different disciplines within mathematics have given the term different meanings depending on the area of study, so the precise meaning depends on context. A simple example of a curve is the parabola, shown to the right. A large number of other curves have been studied in multiple mathematical fields.