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Chapter 4: Graphing Features
56
7. At the second line, press C to
clear any entries, then enter "3.5
1.2X" to represent the Orange Cab's
fare system. When done entering
the equation, press E. The two
equations are now ready to graph.
8. Press G to draw the graphs.
To draw a graph, "=" must be highlighted. If not, move the
cursor to "=" of the targeted equation and press E to draw
a graph, and press E again not to draw a graph.
Graph Basics
The graph examples in this exercise are called X-Y graphs. An
X-Y graph is quite useful for clearly displaying the relationship
between two variables.
9. Let's take a look at the graph. The
vertical axis represents the Y value,
while X is represented by the
horizontal axis. It appears that the
two diagonal lines cross at the point
where the X value is somewhere
between 2 and 3, indicating that Orange Cab costs less than
the other, after 3 miles of travelling.
10. Next, press T to find the values
per graph increment. When the
travelling distance is 2 miles, the
Tomato Cab charges 30 cents less
overall than the Orange Cab, but it
costs 30 cents more at 3 miles. To
make the X increment smaller, press @ y.
11. When the Table setting window
appears, move the cursor down to
"TBLStep", type . 5, and
press E. Now the Y values will
be sampled at every 0.5 mile.
12. Press T to show the table
again. It indicates that when the X value is 2.5, both Y1 and Y2
values are 6.5. It is now clear that if you are travelling 2.5
miles or more, the Orange Cab costs less.
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