HP 35s Scientific Calculator - Manual (Page 235)

Solving and Integrating Programs 15-1
15
Solving and Integrating Programs
Solving a Program
In chapter 7 you saw how you can enter an equation — it's added to the equation
list — and then solve it for any variable. You can also enter a program that
calculates a function, and then solve it for any variable. This is especially useful if
the equation you're solving changes for certain conditions or if it requires repeated
calculations.
To solve a programmed function:
1. Enter a program that defines the function. (See "To write a program for SOLVE"
below.)
2. Select the program to solve: press  
label. (You can skip this step if
you're re–solving the same program.)
3. Solve for the unknown variable: press  variable.
Notice that FN= is required if you're solving a programmed function, but not if
you're solving an equation from the equation list.
To halt a calculation, press  or  and the message  will
appear in line 2. The current best estimate of the root is in the unknown variable;
use
  to view it without disturbing the stack. To resume the calculation,
press  .
To write a program for SOLVE:
The program can use equations and ALG or RPN operations — in whatever
combination is most convenient.