HP 15c Collector's Edition User Manual

Appendix E: A Detailed Look at f 257
Obtaining the Current Approximation to an Integral
When the calculation of an integral is requiring more time than you care
to wait, you may want to stop and display the current approximation. You
can obtain the current approximation, but not its uncertainty.
Pressing ¦ while the HP 15c is calculating an integral halts the
calculation, just as it halts the execution of a running program. When you
do so, the calculator stops at the current program line in the subroutine
you wrote for evaluating the function, and displays the result of executing
the preceding program line. Note that after you halt the calculation, the
current approximation to the integral is not the number in the X-register
nor the number in any other stack register. Just as with any program,
pressing ¦ again starts the calculation from the program line at which
it was stopped.
The f algorithm updates the current approximation and stores it in the
LAST X register after evaluating the function at each new sample point.
To obtain the current approximation, therefore, simply halt the
calculator, single-step if necessary through your function subroutine until
the calculator has finished evaluating the function and updating the
current approximation. Then recall the contents of the LAST X register,
which are updated when the n instruction in the function subroutine
is executed.
While the calculator is updating the current approximation, the display is
blank and does not show running . (While the calculator is executing your
function subroutine, running is displayed.) Therefore, you might avoid
having to single-step through your subroutine by halting the calculator at
a moment when the display is blank.
In summary, to obtain the current approximation to an integral, follow the
steps below.
1. Press ¦ to halt the calculator, preferably while the display is
blank.
2. When the calculator halts, switch to Program mode to check the
current program line.
 If that line contains the subroutine label, return to Run mode
and view the LAST X register (step 3).

HP 15c Collector's Edition Specifications

General

Model	HP 15c Collector's Edition
Category	Calculator
Type	Scientific
Power Source	Battery
Manufacturer	HP
Display	LCD
Functions	complex numbers, matrix operations

Summary

Introduction

This Handbook

Outlines the structure of the manual, detailing its parts and how to use it for learning.

The HP Community

Discusses user groups and websites for HP calculator enthusiasts and information sharing.

Part I: HP 15c Fundamentals

Section 1: Getting Started

Covers basic operations like powering on, keyboard layout, and primary/alternate functions.

Section 2: Numeric Functions

Explains essential numeric operations including logs, trig, powers, and conversions.

Section 3: The Automatic Memory Stack, LAST X, and Data Storage

Details the RPN stack, LAST X register, and data storage operations.

Part II: HP 15c Programming

Section 6: Programming Basics

Introduces core programming concepts: creating, loading, running programs, and memory.

Section 8: Program Branching and Controls

Covers controlling program flow using branching, loops, and conditional tests.

Part III: HP 15c Advanced Functions

Section 11: Calculating With Complex Numbers

Covers entering, manipulating, and performing calculations with complex numbers.

Section 12: Calculating With Matrices

Explains matrix operations, including dimensioning, element access, and calculations.

Section 13: Finding the Roots of an Equation

Details using the SOLVE function for numerical root finding and equation solving.

Section 14: Numerical Integration

Explains how to perform numerical integration using the ∫f(x)dx key and subroutines.

Appendix A: Error Conditions

Error 8: No Root

Explains the error when the SOLVE function cannot find a root.

Error 0: Improper Mathematics Operation

Lists and explains errors related to mathematical operations and illegal arguments.

Appendix D: A Detailed Look at SOLVE

How SOLVE Works

Explains the numerical technique and logic behind the SOLVE algorithm.

Finding Several Roots

Discusses methods for finding multiple roots of an equation using the SOLVE function.