# Introduction to Graphing

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Introduction to Graphing
Section 3.1 Introduction to Graphing

The Rectangular Coordinate System
Page 160 The Rectangular Coordinate System One common way to graph data is to use the rectangular coordinate system, or xy-plane. In the xy-plane the horizontal axis is the x-axis, and the vertical axis is the y-axis. The axes intersect at the origin. The axes divide the xy-plane into four regions called quadrants, which are numbered I, II, III, and IV counterclockwise

Example Page 161 Plot the following ordered pairs on the same xy-plane. State the quadrant in which each point is located, if possible. a. (4, 3) b. (3, 4) c. (1, 0) Solution a. (4, 3) Move 4 units to the right of the origin and 3 units up. b. (3, 4) Move 3 units to the left of the origin and 4 units down. c. (1, 0) Move 1 unit to the left of the origin. Quadrant I Quadrant III Not in any quadrant

Example Page 161 Frozen pizza makers have improved their pizzas to taste more like homemade. Use the graph to estimate frozen pizza sales in 1994 and Solution a. To estimate sales in 1994, locate 1994 on the x-axis. Then move upward to the data point and approximate its y-coordinate. about \$2.1 billion in sales

Example (cont) Page 161 Frozen pizza makers have improved their pizzas to taste more like homemade. Use the graph to estimate frozen pizza sales in 1994 and Solution b. To estimate sales in 2000, locate 2000 on the x-axis. Then move upward to the data point and approximate its y-coordinate. about \$3.0 billion in sales

Scatterplots and Line Graphs
Page 162 Scatterplots and Line Graphs If distinct points are plotted in the xy-plane, then the resulting graph is called a scatterplot.

Example Page 162 Make a scatterplot of the data in the following table, which lists the price of a first-class postage stamp for selected years. Year 1980 1990 2000 2010 Price (cents) 15 25 33 44

Page 163 Line Graphs Sometimes it is helpful to connect consecutive data points in a scatterplot with line segments. This creates a line graph.

Example Page 163 Use the data in the table to make a line graph. Solution Plot the points and then connect consecutive points with line segments. x 3 2 1 1 2 3 y 4

Example Page 164 Use the figure to answer the questions. a. Which 10-year period had the greatest increase in energy consumption? 1970 to 1980 b. Estimate the energy consumption in About 310 million Btu

DONE

Objectives Tables and Graphs The Rectangular Coordinate System
Scatterplots and Line Graphs