# CBSE Class 11-commerce Maths Introduction to Three Dimensional Geometry

#### Introduction to 3-D Geometry

An octant is one of the eight divisions of a Euclidean three-dimensional coordinate system.

There is one to one correspondence between the points in space and ordered triplet (x,y,z) of real numbers.

The coordinates of points on the x axis are of the type (x,0,0), on the y axis are (0,y,0) and on the z axis are (0,0,z)

The x coordinate of the point in the YZ plane is zero, Z-coordinate of a point in the XY plane is zero and y-coordinate in the XZ plane is also zero.#### Distance Formula:3-D Geometry

Three points A, B and C are collinear, if sum of any two of the distances between them is equal to the third distance i.e. either if AB+BC=AC or if AC+CB=AB or if CA+AB=CB.

The distance of any point from the XY plane = | z coordinate | and similarly for the plane XZ and YZ.#### Section Formula: 3- D Geometry

Section formula for the internal and external division of a line segment. Midpoint formula. Problems based on these applications.