This unit looks at some of the ways that we represent points, lines and planes in mathematics. It revises coordinate geometry in two-dimensional Euclidean space, extends these ideas to three-dimensional Euclidean space, introduces the idea of a vector and the algebra of vectors. It covers the dot product of two vectors, and how to use it to determine the general form of the equation of a plane in three-dimensional Euclidean space. It discusses conics as the curves of intersection of double cones and planes in three-dimensional space. The focus-directix definitions of the non-degenerate conics, the ellipse, the parabola and the hyperbola, are given.One subsection is intended to be studied in conjunction with an audio, available in the Linear Algebra Block Pack (order code M208/MMPLA).