EE Pro for TI-89, 92 Plus
Appendix A - Frequently Asked Questions
3
Q. The calculated angle or radian frequency result isn’t correct.
A. Check to be sure the
3
settings list degrees or radians for angle units and make sure it matches the units
of your entered value or desired value. Secondly, if the result is greater than 2
π
or less than -2
π
(
result
≥
360
o
),
the TI solve(...) function may be generating a non principal solution. A principal solution is defined as a value
between 0 and 2
π
(or between 0 and 360
o
). A non principal solution can be converted to a principal solution by
adding or subtracting integer multiples of 2
π
(or 360
o
) until the remainder is within the range of 0 and 2
π
(or 0 and
360
o
). The remainder is the principal solution.
Example: Imagine solving the equation sin( )
.
x
=
0 5 . Non principle solutions include: 30°, 390°, -330°, 750°, etc.,
but the principal solution is 30°.
Q. The solution for an analysis function is expressed in symbolic terms or variables, whereas a numerical value
was expected. Why?
A. If a variable name is entered as an input, EE•Pro will calculate a solution in symbolic form. In cases where a
parameter entry is left blank, the variable’s name will be used in a symbolic computation. A name cannot be
entered which is identical to the variable name (i.e.: C for capacitance) instead, leave the entry blank.
Q. Units are not displayed in Analysis computations. Why?
A. The Analysis section incorporates methods for calculation which are unique to each topic in analysis (as
opposed to Equations which uses similar methods of calculation in all of the sections). Unit management was
omitted for simplicity. All entries and computed results in Analysis are assumed to be in common SI units (F, m,
A,
Ω
, etc.) which are stated in the status line for each parameter. In some cases, variables will be expressed in
units arbitrarily chosen by the user (example: The variable len in Transmission Lines can be entered in km, m,
miles however the answers will be expressed in units of len).
If a value is entered that is inconsistent with the expected data type, an error dialog will appear which lists the
entry name, the description, and the expected data type(s). See Appendix E for details on error messages.
Q. What is the multiple graph feature in Capital Budgeting and how do I get it to plot several projects
simultaneously?
A. Activating the multiple graph feature allows successive graphs to be overlayed on the same. To do this, the
graphing execution must be repeated each time a new project is plotted.
1. Make sure the cash flows for all the named projects have been entered.
2. Enable
the
Multiple Graphs
feature by highlighting and pressing the
¸
key.
3. Select the name of a project you wish to graph and press
…
.
4. To overlay a second project on the first, select a different project name and press
…
to graph.
5. Repeat step 4 each time a new project is to be graphed on top of previously plotted functions.
A.4 Equations Questions
These are some common questions about the Equations section of EE•Pro.
Q. There are already values stored in some of my variables. How do I clear or use those values?
A. These values remain from previous solving operations. It is okay to ignore the values. As long as they aren’t
selected ‘
é
‘ they will be overwritten by new solutions. If you want to reset the values, clear one or all of the
variables. A value can be re-used in a computation by highlighting the displayed value and pressing
¸
twice.
Q. Why do the values of the entered or calculated results change when the Units feature is deactivated in the
‡
options menu?