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 8.1 The Coordinate Plane 8.2 Lines and Distance 8.3 Graphing Linear Inequalities 8.4 Other Important Graphs and Equations 8.5 Vectors 8.6 Coordinate Space

 8.7 Polar Coordinates 8.8 Parametric Equations 8.9 Key Formulas 8.10 Review Questions 8.11 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. Any other 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 is the point (0, 0). Following is a figure of the coordinate plane with a few points labeled with their coordinates:
As you can see from the figure, each of the points on the coordinate plane receives a pair of coordinates: (x, y). The first coordinate in a coordinate pair is called the x-coordinate. The x-coordinate of a point is its 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.