The moving power of mathematical invention is not reasoning but imagination. – A.DEMORGAN
We constantly describe both the shapes and positions of three dimensional objects. For example, one simple way to describe a 3D object is to approximate its shape as a mesh of triangles. Each triangle is de?ned by three vertices, and the positions of each of these vertices will have to be described by three coordinates [x,y,z]t.In this chapter, we shall study the direction cosines and direction ratios of a line joining two points and also discuss about the equations of lines and planes in space under different conditions, angle between two lines, a line and a plane, shortest distance between two skew lines and distance of a point from a plane.Lower level geometry of planes and graphical two dimensional coordinates moves into a three dimensional space in three dimensional geometry.
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