Math 101 Intermediate Algebra    The Cartesian Coordinate System Chapter 3, Section 1 Cartesian Coordinates--Overview Locate points in 2-D by specifying where the point is relative to the Origin. Any point may be specified by an ordered pair (described below). The horizontal line labeled "x" is the x-axis. The vertical line labeled "y" is the y-axis. Quadrants are regions of the plane relative to the origin. Quadrant I: x > 0 and y > 0 Quadrant II: x < 0 and y > 0 Quadrant III: x < 0 and y < 0 Quadrant IV: x > 0 and y < 0 Ordered Pairs (x, y) Any point in 2-D may be located by an ordered pair (x, y). The x-coordinate, x, is the value on the x-axis vertically above or below the point. The y-coordinate, y, is the value on the y-axis horizontally right or left of the point. The order is that the x-coordinate is listed first and the y-coordinate is listed second. Distance Formula The distance formula gives the distance, d, between 2 given points (x1, y1) and (x2, y2). Distance is always non-negative. Midpoint Formula The midpoint formula gives an ordered pair that is the point halfway between 2 given points (x1, y1) and (x2, y2).