Subtracting Points

The formula for calculating a displacement vector can be written as:

Displacement from point S (start) to point F (finish) =

F - S = ( Xf , Yf )T - ( Xs , Ys )T = ( Xf-Xs , Yf-Ys )T

In this operation two points are used to produce one vector:

Don't skip over this observation with a yawn. Think a few careful thoughts now to avoid confusion later on.

It is slightly odd that a "minus" with two objects of one type produces an object of another type.