HP 40gs hp 40gs_user's guide_English_E_HDPMSG40E07A.pdf - Page 96

hp40g+.book Page 10 Friday, December 9, 2005 1:03 AM Using variables in equations You can use any of the real variable names, A to Z and θ. Do not use variable names defined for other types, such as M1 (a matrix variable). Home variables HINT All home variables (other than those for aplet settings, like Xmin and Ytick) are global, which means they are shared throughout the different aplets of the calculator. A value that is assigned to a home variable anywhere remains with that variable wherever its name is used. Therefore, if you have defined a value for T (as in the above example) in another aplet or even another Solve equation, that value shows up in the Numeric view for this Solve equation. When you then redefine the value for T in this Solve equation, that value is applied to T in all other contexts (until it is changed again). This sharing allows you to work on the same problem in different places (such as HOME and the Solve aplet) without having to update the value whenever it is recalculated. As the Solve aplet uses existing variable values, be sure to check for existing variable values that may affect the solve process. (You can use CLEAR to reset all values to zero in the Solve aplet's Numeric view if you wish.) Aplet variables Functions defined in other aplets can also be referenced in the Solve aplet. For example, if, in the Function aplet, you define F1(X)=X2+10, you can enter F1(X)=50 in the Solve aplet to solve the equation X2+10=50. 7-10 Solve aplet