# Repeating Calculations; Creating An Expression - HP -28S Manual

4
Repeating Calculations
In this chapter you'll create an expression containing numerical vari-
ables and then use a calculator feature called the Solver to evaluate
the expression for various values of the numerical variables.
In chapter 2 you made a calculation by keying in an expression that
contained
numbers
and then evaluating the expression. In this chapter
you'll create an expression by calculating on the stack, using
names
as
symbolic arguments. You'll use the Solver to assign values to the vari-
ables and evaluate the expression. Each time you evaluate the
expression, the calculation is made with the current values of the vari-
ables. If you change the value of one or more variables, you can
simply evaluate the expression again to recalculate with the new
values.
In chapter 3 you created numerical variables and a program variable.
In this chapter you'll create expression variables and name variables.
(Remember, any object can be stored in a variable.) You'll also learn
directories,
which are sets of variables.
Creating an Expression
We'll repeat the resistance calculation from "Chain Calculations" in
chapter 2, only this time we'll use names, rather than numbers, as
arguments. Recall that the formula for the circuit is:
1
1
+
1
58
4: Repeating Calculations