1) If then the magnitude or length or norm or absolute value of is
2) A vector of unit magnitude is the unit vector. If is a vector then the unit vector of is denoted by and
3) Important unit vectors are , where
4) The components of unit vectors of are called the direction cosines of , denoted by and
5) If, then are called directional angles of the vectors and
6) If and are the two points, then
7) If and then
8) If and is a scalar number, then.
9) In vector addition
IV. , is the additive identity in vector addition.
V. , is the inverse in vector addition.