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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.5.88a

88. Given that x>0, find the maximum value, if any, of
a. x^(1/x)

Guida verificata passo dopo passo
1
Identify the function to maximize: \(f(x) = x^{\frac{1}{x}}\) with the domain \(x > 0\).
Rewrite the function using the natural logarithm to simplify differentiation: consider \(y = x^{\frac{1}{x}}\), then take the natural log to get \(\ln y = \frac{1}{x} \ln x\).
Differentiate both sides with respect to \(x\) using implicit differentiation: \(\frac{1}{y} \frac{dy}{dx} = \frac{d}{dx} \left( \frac{\ln x}{x} \right)\).
Apply the quotient rule to differentiate \(\frac{\ln x}{x}\): \(\frac{d}{dx} \left( \frac{\ln x}{x} \right) = \frac{(\frac{1}{x}) \cdot x - \ln x \cdot 1}{x^2} = \frac{1 - \ln x}{x^2}\).
Set the derivative \(\frac{dy}{dx}\) equal to zero to find critical points: since \(\frac{dy}{dx} = y \cdot \frac{1 - \ln x}{x^2}\), solve \(1 - \ln x = 0\) to find \(x = e\). Then analyze the behavior around \(x = e\) to determine if it is a maximum.

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Function Analysis and Domain

Understanding the behavior of the function f(x) = x^(1/x) for x > 0 is essential. This involves recognizing the domain restrictions and how the function behaves as x approaches 0 and infinity, which helps in identifying potential maxima or minima.
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Differentiation and Critical Points

To find the maximum value of the function, we use differentiation to find critical points where the derivative equals zero or is undefined. These points are candidates for local maxima or minima and are crucial for optimization problems.
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Logarithmic Differentiation

Since the function involves a variable exponent, logarithmic differentiation simplifies the process. Taking the natural logarithm of f(x) = x^(1/x) transforms it into a product, making it easier to differentiate and solve for critical points.
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Logarithmic Differentiation