Imagine you are at a point A and you want to go to a point B. You must travel in the direction that takes you from point A to point B. You can plot the positions of A and B, and find the bearing from A to B by superimposing on A a compass, with angles labelled from 0 to 360 degrees.
We can then just read off the bearing from A to B.
If A and B are given as position vectors
and
then it is useful to find the vector
and plot it, on a compass with the centre of the compass acting as A.
The bearing will be given by
if
and
are both positive
if
is negative and
is positive
if
and
are both negative
if
is positive and
is negative