Why Do Different Solving Methods Yield Different Results for (sin(x)/x) = x?

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Discussion Overview

The discussion revolves around the equation (sin(x)/x) = x and the discrepancies observed when solving it using different methods. Participants explore the implications of numerical methods, computer limitations, and representation of numbers in computational systems.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that graphically, the solution to (sin(x)/x) = x appears to be zero, but questions arise when considering (sin(x)/x) = 1, which suggests a nonzero solution.
  • Another participant argues that computers have inherent limitations that prevent them from calculating exact solutions, leading to discrepancies in results.
  • It is mentioned that different representations of functions can yield different computational results, highlighting the challenges of numerical methods.
  • Examples are provided of numbers like pi and 0.1 that cannot be represented exactly in a binary system, which contributes to the inaccuracies in computational results.
  • A later reply clarifies that the issue of representation is specific to binary computers, noting that decimal computers do not face the same limitations.

Areas of Agreement / Disagreement

Participants express differing views on the nature of computational limitations and the implications for solving equations. There is no consensus on the resolution of the discrepancies observed in the solutions.

Contextual Notes

Participants discuss the limitations of numerical methods and the representation of irrational numbers, but do not resolve the implications of these limitations on the specific equation in question.

Who May Find This Useful

This discussion may be of interest to those exploring numerical methods, computational limitations, and the representation of mathematical functions in different computing systems.

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Computers have inherent limitations. The answer is in fact still zero.

When a computer uses a numerical method to approximate the solution to an equation such as the one you gave, it simply can not calculate the answer exactly. It turns out that different representations of functions can give different computational results, which you have just seen.
(Why are computers ultimately inaccurate? Consider an irrational number like pi, 3.1415926... etc. Pi never ends. Well computers are inherently discrete systems and so a computer can NEVER represent an infinite decimal like pi. A computer only has so many bits and can only represent rational numbers ultimately. The computer's number line has "gaps".
Couple this limitation of computers with the following fact. It turns out that there are way more irrationals than there are rationals on the real number line. So much more in fact that if you picked a number at random off of the real number line, the probability that you would pick a rational is 0. Not 0.0000000001. Flat out zero.)

Moral of the Story:
This is one of the reasons computers are not the end all be all. A good thing to know.
 
Yet another example of a number that a digital computer cannot represent exactly is .1. When converted to binary it becomes an infintly repeating decimal and must be rounded off.
 
Integral said:
Yet another example of a number that a digital computer cannot represent exactly is .1.

You mean, "a binary computer" not "a digital computer". There are decimal computers (in, e.g., many calculators) that do not have this issue. (And of course they can be emulated even on binary computers, as in the Decimal type in C#.)
 

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