# *Describing a vector

***Describing a vector**

A vector can be expressed as infinite no. of components in 2D or 3 D, however generally a vector is expressed as the resolution of three mutually perpendicular components

a, b & c along x, y & z axis respectively.

Here (a, b, c) are also called direction ratios of .

Length of a vector is called its magnitude .. Magnitude of is described as,

Let makes angle θx, θy & θz with the x, y & z axis respectively. cos of these angels are called direction ratios of & usually expressed in terms of symbols (l, m, n) & are related to direction ratios as

Magnitude of a unit vector is unity i.e.