OA,OB = x
2, being distances, carrying signs, along an axis, the “Bearing” of B with respect to A (called a vector, or step, or displacement) is given by AB = OB – OA = x
2 – x
1 in all cases, and is independent of the position of O.
If we wish to add two such steps, a construction is necessary, viz. they are placed “ end on ” in either order; and the sum is dependent on the position of O ; if M be the mid-point of AB, the sum = 20M.