I have a 50G, but it should be similar to a 49G+.

The INTVX and DERVX commands (and other "VX" commands, such as SOLVEVX and SIGMAVX), use whatever independent variable is stored in {HOME CASDIR VX}. The default value for VX is "X", but you can change this to "Y" or "t" or any other variable, by adjusting the "Indep var" setting in MODE CAS. For example:

If you have X in VX, then INTVX(8) returns 8X

If you have Y in VX, then INTVX(8) returns 8Y

If you have t in VX, then INTVX(8) returns 8t

Since the VX commands automatically use whatever independent variable in VX, you don't need to specify the independent variable.

Alternatively, you can use DERIV instead of DERVX, or RISCH instead of INTVX. However, these commands ignore VX, and expect you to specify the independent variable. For example:

RISCH(8,X) returns 8X

RISCH(8,Y) returns 8Y

RISCH(8,t) returns 8t

DERIV and RISCH might be preferable if you were working with several different independent variables. Suppose, for example, that you were taking partial derivatives of functions with respect to X, Y, and Z. If you used DERVX, you would have to keep resetting the variable in VX. It would probably be easier to use DERIV instead.

The term "RISCH" presumably refers to the Risch algorithm for finding antiderivatives

*Edited: 10 Jan 2007, 4:42 p.m. *