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 8.1 The Coordinate Plane 8.2 Lines and Distance 8.3 Lines 8.4 Graphing Linear Inequalities 8.5 Other Important Graphs and Equations

 8.6 Coordinate Space 8.7 Key Formulas 8.8 Review Questions 8.9 Explanations
The Coordinate Plane
The coordinate plane is a plane determined by two perpendicular lines, the x-axis and the y-axis. The x-axis is the horizontal axis, and the y-axis is the vertical axis. Every point in the plane can be stated by a pair of coordinates that express the location of the point in terms of the two axes. The intersection of the x- and y-axes is designated as the origin, and its point is (0, 0).
As you can see from the figure, each of the points on the coordinate plane is expressed by a pair of coordinates: (x, y). The first coordinate in a coordinate pair is called the x-coordinate. The x-coordinate is the point’s location along the x-axis and can be determined by the point’s distance from the y-axis (where x = 0). If the point is to the right of the y-axis, its x-coordinate is positive, and if the point is to the left of the y-axis, its x-coordinate is negative. The second coordinate in a coordinate pair is the y-coordinate. The y-coordinate of a point is its location along the y-axis and can be calculated as the distance from that point to the x-axis. If the point is above the x-axis, its y-coordinate is positive, and if the point is below the x-axis, its y-coordinate is negative.