Question: how to find the displacement vector between two points?
Answer: The displacement vector d from P1 to P2 may be written as d = (x2 - x1)i + (y2 - y1)j. The displacement d is (x2 - x1) units in the x-direction plus (y2 - y1) units in the y-direction. The magnitude of the displacement is d = ((x2 - x1)2 + (y2 - y1)2)½. This follows from the Pythagorean theorem.