We can use the Pythagorean Theorem to find the distance between any two points in a plane. To find the length d(A, B) of the line segment AB, consider the point C(x,, y) which is on the same vertical line segment as point A and the same horizontal line segment as point B. The triangle formed by points A, B and C is a right triangle whose hypotenuse has length d (A, B). The horizontal leg of the triangle has length a = |x2, - x1| while the vertical leg of the triangle has length b = |y2,-y1|
The Distance Formula: The distance between any two points A(x1,y1) and B(x2, y2) is given by the formula d(A,B) = (in root) square of(x2-x1) + square of (y2-y1)