A position vector is any vector that is placed extending from the origin. Position vectors are often denoted by , for example, to identify the vector that points from the origin to a point A.
Let and be the position vectors that point from the origin to the points A and B respectively. We can then find the vector that points from A to B:
The length of a vector can be found using pythagoras.
The length of this vector can then be found using pythagoras: