4.1 The Coordinate Plane

• In mathematics, points are located in reference to two perpendicular lines called axes.

The Coordinate Plane

• Points in the coordinate plane are named by ordered pairs of the form (x , y).

• The first number, or x-coordinate, corresponds to the numbers on the x-axis.

• The second number, or y-coordinate, corresponds to the numbers on the y-axis.

• The origin, labeled O, has coordinates (0 , 0).

Name an Ordered Pair• Write the ordered pair for point G.

• The ordered pair for point G is (-4 , 3).• This can also be written as G(-4 , 3).

Quadrants• The x-axis and y-axis separate the coordinate

plane into four regions, called quadrants.

• Notice which quadrants contain positive and negative x-coordinates, and which quadrants contain positive and negative y-coordinates.

• The axes are not located in any of the quadrants.

Quadrants

Identify Quadrants• Write ordered pairs for points A, B, C, and D. Name

the quadrant in which each point is located.

Graph Points• To graph an ordered pair means to draw a dot

at the point on the coordinate plane that corresponds to the ordered pair.

• This is sometimes called plotting a point.

• When graphing an ordered pair, start at the origin.

• The x-coordinate indicates how many units to move right (positive) or left (negative).

• The y-coordinate indicates how many units move up (positive) or down (negative).