hp40g+.book Page 5 Friday, December 9, 2005 1:03 AM
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
Selecting the independent variable
Selecting the modulus
Approximate vs. Exact mode
Many of the functions provided by CAS use a predetermined 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.
The MODULO option on CAS MODES screen lets you specify the modulo you want to use in modular arithmetic. The default value is 13.
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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