HP 40gs hp 40gs_user's guide_English_E_HDPMSG40E07A.pdf - Page 269

hp40g+.book Page 17 Friday, December 9, 2005 1:03 AM • 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 ( ), Equation Writer 15-17