Find the direction cosines of the vector joining the points A(1, 2, –3) and B(–1, –2, 1), directed from A to B.

So, and

Now we want to find the

Now, we have to find the direction cosines which are the coefficients of the unit vector in the direction of .We know that unit vector means that the magnitude of the vector is 1(unit).

It is defined as

So, we find the magnitude of first.

Therefore, The direction cosines of the given vector are .