•  First example:

A = (−1,2); B = (4, 5).  I get: distance between A and B, slope (0.6) and direction of AB, midpoint of AB line AB: (y-2)·(-1-4) = (x+1)·(2-5), or: y = 0.6·(x+1)+2 perp. bis.: y = -5/3·(x-1.5)+3.5 direction vector of AB: (0.8575, 0.5145)     We can draw the figure with this script (or with               this - see the code;  se also here).

•  Second example:

what is the direction vector?

direction:  125.1°;  direction vector:  (-0.5752, 0.8180)