HP 48gII hp 48gII_user's manual_English_E_HDPMSG48E67_V2.pdf - Page 797

A variable called VX exists in the calculator's {HOME CASDIR} directory that takes, by default, the value of 'X'. This is the name of the preferred independent variable for algebraic and calculus applications. For that reason, most examples in this Chapter use X as the unknown variable. If you use other independent variable names, for example, with function HORNER, the CAS will not work properly. The variable VX is a permanent inhabitant of the {HOME CASDIR} directory. There are other CAS variables in the {HOME CASDIR}, e.g., REALASSUME (@REALA), MODULO (@MODUL), CASINFO (@CASIN), etc. You can change the value of VX by storing a new algebraic name in it, e.g., 'x', 'y', 'm', etc. Preferably, keep 'X' as your VX variable for the examples in this manual. Also, avoid using the variable VX in your programs or equations, so as to not get it confused with the CAS' VX. If you need to refer to the x-component of velocity, for example, you can use vx or Vx. Selecting the modulus The Modulo option of the CAS MODES input box represents a number (default value = 13) used in modular arithmetic. More details about modular arithmetic are presented elsewhere. Numeric vs. symbolic CAS mode When the Numeric CAS mode is selected, certain constants pre-defined in the calculator are displayed in their full floating-point value. By default, the _Numeric option is unselected, meaning that those pre-defined constants will be displayed as their symbol, rather than their value, in the calculator display. The following screen shows the values of the constant π (the ratio of the length of the circumference to its diameter) in symbolic format followed by the numeric, or floating-point, format. This example corresponds to the Algebraic operating mode. Page C-3