advertisement

Section 3.1 Introduction to Graphing Copyright © 2013 Pearson Education, Inc. The Rectangular Coordinate System Page 160 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. Quadrant I b. (3, 4) Move 3 units to the left of the origin and 4 units down. Quadrant III c. (1, 0) Move 1 unit to the left of the origin. 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 2000. 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 2000. 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 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. 1980 1990 2000 15 25 33 2010 44 Postage Stamp Prices Price in cents Year Price (cents) 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 1970 1980 1990 2000 2010 2020 Year Line Graphs Page 163 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. x y 3 3 2 4 1 0 0 3 1 2 2 4 3 3 Solution Plot the points and then connect consecutive points with line segments. 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 2010. About 310 million Btu DONE Objectives • Tables and Graphs • The Rectangular Coordinate System • Scatterplots and Line Graphs