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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 7, Problem 7.2.23

In Exercises 7–38, find the derivative of y with respect to x, t, or θ, as appropriate.
23. y = ln(x)/(1+ln(x))

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1
Identify the function given: \(y = \frac{\ln(x)}{1 + \ln(x)}\). We need to find \(\frac{dy}{dx}\) since the variable is \(x\).
Recognize that this is a quotient of two functions: numerator \(u = \ln(x)\) and denominator \(v = 1 + \ln(x)\).
Recall the quotient rule for derivatives: \(\frac{d}{dx} \left( \frac{u}{v} \right) = \frac{v \cdot u' - u \cdot v'}{v^2}\).
Compute the derivatives of numerator and denominator separately: \(u' = \frac{d}{dx} \ln(x) = \frac{1}{x}\) and \(v' = \frac{d}{dx} (1 + \ln(x)) = \frac{1}{x}\).
Substitute \(u\), \(v\), \(u'\), and \(v'\) into the quotient rule formula to express \(\frac{dy}{dx}\) as \(\frac{(1 + \ln(x)) \cdot \frac{1}{x} - \ln(x) \cdot \frac{1}{x}}{(1 + \ln(x))^2}\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Derivative of the Natural Logarithm Function

The derivative of ln(x) with respect to x is 1/x. This fundamental rule is essential when differentiating expressions involving natural logarithms, as it allows us to handle the logarithmic part of the function accurately.
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Derivative of the Natural Logarithmic Function

Quotient Rule

The quotient rule is used to differentiate functions expressed as one function divided by another. It states that the derivative of f(x)/g(x) is (g(x)f'(x) - f(x)g'(x)) / [g(x)]², which is crucial for differentiating y = ln(x) / (1 + ln(x)).
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Chain Rule

The chain rule helps differentiate composite functions by multiplying the derivative of the outer function by the derivative of the inner function. It is important here because ln(x) appears inside another function, requiring careful application of this rule.
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Intro to the Chain Rule