HP 40gs - Manual (Page 187)

Computer Algebra System (CAS) 14-5
CAS modes
The modes that determine
how CAS operates can be
set on CAS MODES screen.
To display CAS MODES
screen, press:
·To navigate through the options in CAS MODES screen,
press the arrow keys.
To select or deselect a mode, navigate to the appropriate
field and press
until the correct setting is displayed
(indicated by a check mark in the field). For some settings
(such as
INDEP VAR and MODULO ), you will need to press
to be able to change the setting.
Press to close CAS MODES screen.
N O T E You can also set CAS modes from within the Equation
Writer. See “Configuration menus” on page 15-3 for
information.
Selecting the
independent
variable Many of the functions provided by CAS use a pre-
determined independent variable. By default, that
variable is the letter X (upper case) as shown in CAS
MODES screen above. However, you can change this
variable to any other letter, or combination of letters and
numbers, by editing the
INDEP VAR field in CAS MODES
screen. To change the setting, press , enter a new
value and then press .
The variable VX in the calculator's {HOME CASDIR}
directory takes, by default, the value of 'X'. This is the
name of the preferred independent variable for algebraic
and calculus applications. If you use another independent
variable name, some functions (for example, HORNER)
will not work properly.
Selecting the
modulus The MODULO option on CAS MODES screen lets you
specify the modulo you want to use in modular arithmetic.
The default value is 13.
Approximate vs.
Exact mode When the APPROX mode is selected, symbolic operations
(for example, definite integrals, square roots, etc.), will be
calculated numerically. When this mode is unselected,
exact mode is active, hence symbolic operations will be
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