We can also add B to A , Fig. 2–4 a , using the triangle rule , which is a
special case of the parallelogram law, whereby vector B is added to
vector A in a “head-to-tail” fashion, i.e., by connecting the head of A to
the tail of B , Fig. 2–4 b . The resultant R extends from the tail of A to the
head of B . In a similar manner, R can also be obtained by adding A to B ,
Fig. 2–4 c . By comparison, it is seen that vector addition is commutative;
in other words, the vectors can be added in either order, i.e.,
R = A + B = B + A .