Calculator Issues
The following material describes features of the TI-83
calculator. Other TI's will be similar. You should be familiar with the
workings of your own particular calculator. At the very least, your calculator
needs to be able to graph functions in various sized windows and it needs to be
able to estimate zeros of functions.
Menus:
Many of the functions of the TI-83 are accessed through menus.
Often, an initial key like MATH brings up several submenus (MATH,
NUM, CPX, and PRB in this case). The particular functions
are then accessed by the arrow keys. The most commonly used math functions are
available directly, as with LN and 2nd ex. The
MODE menu has several important functions. Selecting Normal and
2 will cause your answers to be displayed with 2 digits to the right of
the decimal. Func should also be selected for graphing in function
mode. We might also have use for Horiz and G-T, two display
modes involving graphs with additional information.
Graphing:
It is important to be able to graph functions is various
sized windows. The Y= menu is used to store formulas for functions
that are then graphed by the GRAPH key. The three Plot items
in the Y= menu should not be selected. If they are, move the cursor
over the ones that are selected and deselect them by pressing ENTER.
Next, the =signs in the Y= menu are used to indicate which
of the ten Yi formulas are to be graphed. They all behave
as toggles-you just move the cursor over the equal sign and hit enter to
switch the state between include or omit. The line icon at the beginning
of each entry of the Y= menu can be used to change the graphing
style. Point mode can be useful for functions that jump. The line mode
would end up including some vertical lines that are not really part of
the graph.
Windows:
The viewing window is the portion of the coordinate plane
that will be displayed when doing a graph. The region is defined in the
WINDOW menu by Xmin, Xmax, Ymin, and Ymax.
The variables Xscl and Yscl are used to control the tick marks
indicating the scales along the axes. Choosing a good viewing window is a bit
of an art. You want a window that shows all the "important features", but
until you have the graph it's hard to know if it really does. The ZOOM
menu has some useful features. ZoomFit will automatically adjust
Ymin and Ymax to include all of the graph. Zoom In and
Zoom Out will adjust the viewing window based on the zoom factors.
These factors are set in the MEMORY submenu of ZOOM.
Functions:
The most important thing to remember when entering functions
in the Y= menu is order of operations. Calculators generally follow
the standard order of operations convention: firstly parentheses, secondly
exponentiation, thirdly multiplication and division working left to right,
and fourthly addition and subtraction working left to right. When you enter
something like 5^2*x you probably don't mean 25*x but that is
what the calculator will understand. Parentheses can always be used to remove
any ambiguity. In this case, you probably wanted 5^(2*x).
The CALC menu:
The real graphical power of the TI-83 shows up in the CALC menu.
Once a function has been entered and graphed, the CALC menu provides
options that compute particular values, zeros, locations of minima and maxima,
intersection points, numerical derivatives, and definite integrals. Some of
these features require left and right bounds. These bounds can be entered
graphically, by using the cursor, or numerically.
www.isu.edu/~laquerht/
Latest revision: 1/13/2004