Can the Integration of x^x be Solved Conventionally?

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Discussion Overview

The discussion centers around the integration of the function f(x) = x^x, specifically whether it can be solved using conventional methods. Participants explore the challenges associated with finding a closed form for the integral and discuss related concepts such as differentiation.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant expresses uncertainty about the possibility of integrating f(x) = x^x conventionally and seeks input from others.
  • Another participant asserts that the integral cannot be expressed in a closed form of elementary functions, comparing it to other functions like e^(x²) and sqrt(sin(x)).
  • A different participant provides a method for finding the derivative of f(x) = x^x using logarithmic differentiation, detailing the steps involved in the process.
  • A participant shares a graph of the integral from 0 to x of u^u, indicating an interest in visualizing the function despite the lack of a closed form for the integral.

Areas of Agreement / Disagreement

Participants generally agree that the integral of x^x cannot be expressed in a closed form of elementary functions. However, there is no consensus on the implications of this for the broader discussion of the function's properties.

Contextual Notes

The discussion highlights the limitations of conventional integration techniques for certain functions and the reliance on graphical representations to understand their behavior.

Quadratic
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A few of my friends and I have been trying to integrate/derive the following:

f(x) = x^x

without success. I'm not sure if it can be done conventionally, but I was wondering if anyone had any thoughts on this one. Thanks.
 
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It cannot be done "conventionally", i.e. you cannot express its primitive in a closed form of elementary functions, which is also the case for e^(x²), sqrt(sin(x)), sin(x)/x, ...
 
While \int x^x dx cannot be expressed in a finite number of elementary functions, derivative of f(x)= x^x can be obtained by logarithmic differentiation: take the log of both sides to get

ln[f(x)]=ln\left( x^x\right) = x ln(x)

now differentiate both sides to get

\frac{f^{\prime}(x)}{f(x)}= ln(x)+1

multiply by f(x) to get

f^{\prime}(x)= f(x)( ln(x)+1) = x^x( ln(x)+1)
 
Attached is a graph of y=\int_0^x u^u du, courtesy of Apple Grapher. :smile:
 

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