HP 40gs - Manual (Page 269)

Equation Writer 15-17
• MODULO contains the value of p for performing
symbolic calculations in Z/pZ or in Z/pZ[X]. You can
change the value of p either with the
MODSTO
command on the MODULAR menu, (by typing, for
example, MODSTO(n) to give p a value of n), or from
CAS MODES screen (see page 14-5).
• PERIOD must contain the period of a function before
you can find its Fourier coefficients.
• PRIMIT contains the primitive of the last integrated
function.
• REALASSUME contains a list of the names of the
symbolic variables that are considered reals. If you’ve
chosen the
Cmplx vars option on the CFG
configuration menu, the defaults are X, Y, t, S1 and
S2, as well as any integration variables that are in
use.
If you’ve chosen the Real vars option on the CFG
configuration menu, all symbolic variables are
considered reals. You can also use an assumption to
define a variable such as X >1. In a case like this,
you use the
ASSUME(X>1) command to make
REALASSUME contain X>1. The command
UNASSUME(X) cancels all the assumptions you have
previously made about X.
To see these variables, as well as those that you’ve
defined in CAS, press
in the Equation Editor
(see “CAS variables” on page 14-4).
The keyboard in the Equation Writer
The keys mentioned in this section have different functions
when pressed in the Equation Writer than when used
elsewhere.
MATH key The key, if pressed in
the Equation Writer, displays
just those functions used in
symbolic calculation. These
functions are contained in
the following menus:
• The five function-containing Equation Writer menus
outlined in the previous section:
Algebra ( ),
hp40g+.book Page 17 Friday, December 9, 2005 1:03 AM