# Chapter Three 3.1 ```Section 3.1
Introduction to
Graphing
Copyright &copy; 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
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.
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.
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.