ABCD is a parallelogram,and
Because vectors can be moved andis parallel to, and the same length as
we can write
Similarly, sinceis parallel to, and the same length as
so we can write
Vectors add in a natural way soand
Suppose now that we find the midpoint of AC and call it M and we find the midpoint of BC and call it N. Because M and N are the midpoints of AC and BC respectively,and
Suppose we want to find the vector vec NM.
We can go from N to C and then from C to M. From N to C isand from C to M is
is since
is against the direction of
Parallel Vectors
Any vector that is a multiple ofis parallel to
so
is parallel to