Cross-Sectional Models And Rates Of Change - Texas Instruments TI-84 Plus Manual

Step 2: Choose values for v and solve for t to obtain points on the 2000 constant-contour
curve. Obtain guesses for the values of v and t from Table 9.2 in the text.
Enter the H ( v, t ) formula in
sure that you use the letters
not . (We are only using
X
a "holding place" for the formula.)
Go to the
SOLVER
equation – 2000. Press
Y1
Have the cursor on the
Press or
5. ▼
cursor to the
T
ALPHA ENTER (SOLVE)
WARNING: The cursor must be on the line corresponding to the unknown variable for the
to solve the equation for that variable. If you do not have a table of values for the
SOLVER
quantities, you should enter several different guesses for the unknown variable to determine
whether there is more than one solution to the equation.
Press , enter another value for v ,
▲
say v = 10 years. Move the cursor to
the line and press
T
. Enter v = 15 and repeat the
(SOLVE)
procedure to solve for t .
Repeat the procedure for v = 20 and
v = 25. Make a table of the values
of v and t as you find these values.
Step 3: Plot the points obtained in Step 2 with pencil and paper. You need to find as
many points as it takes to see the pattern the points are indicating when you plot
them. Connect the points you have plotted with a smooth curve.
You must have a function given to draw a contour graph using the above method. Even
though there may be several functions that seem to fit the data points obtained in Step 2, their
use would be misleading because the real best-fit function can only be determined by substi-
tuting the appropriate values in a multivariable function. The focus of this section is to use
contour graphs to study the relationships between input variables, not to find the equation of a
function to fit a contour curve. Thus, we always sketch the contours on paper rather than with
the calculator.

9.2 Cross-Sectional Models and Rates of Change

For a multivariable function with two input variables, obtain a cross-sectional model by enter-
ing the data in lists
chapters of this Guide . Unless you are told otherwise, we assume that the data are given in a
98
. Be
Y1
and ,
V T
as
Y1
and enter the
ENTER .
line and type
V
to move the
ENTER
line and solve for with
T
.
ALPHA ENTER
and and then fitting the appropriate function as indicated in previous
L1 L2
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Chapter 9