Coordinate system

The coordinate system is often used in geometry. The plane determined by a horizontal number line, called the x-axis, and a vertical number line, called the y-axis, intersecting at a point called the origin. Each point in the coordinate plane can be specified by an ordered pair of numbers, (x,y). The cordinate system is organized to 4 quadrants. In the first quadrant, both (x,y) are positive. In the second quadrant x is negative, while y is positive.In the third quadrant, both (x,y) are negative. Finally, in the fourth quadrant x is positive while y is negative. To find the slope of a line on the coordinate system with points we need to compute . The slope is usually expressed as . Also, there is the point-slope form which states for some real numbers b,x,y. Also, if two lines are perpendicular, then product of the slopes is -1. (For example, the slope could be -3/4 and 4/3.) The coordinate system is also widely useful were right triangle, since there is 90 degrees.