/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 53 Compute the following derivative... [FREE SOLUTION] | 91Ó°ÊÓ

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Compute the following derivatives using the method of your choice. $$\frac{d}{d x}\left[\left(\frac{1}{x}\right)^{x}\right]$$

Short Answer

Expert verified
Question: Find the derivative of the function $$\left(\frac{1}{x}\right)^{x}$$ with respect to x. Answer: The derivative of the given function with respect to x is $$-\frac{\left(\frac{1}{x}\right)^{x}}{x} + \left(\frac{1}{x}\right)^{x}\ln\left(\frac{1}{x}\right)$$

Step by step solution

01

Rewrite the function using ln

To make it easier to differentiate, rewrite the function as follows, using the natural logarithm: Let $$y = \left(\frac{1}{x}\right)^{x}$$. Then, taking the natural logarithm of both sides, we get: $$\ln(y) = \ln\left(\left(\frac{1}{x}\right)^{x}\right) = x\ln\left(\frac{1}{x}\right)$$ This makes it easier to differentiate both sides with respect to x.
02

Differentiate both sides with respect to x

Now, we can use implicit differentiation to find the derivative of y with respect to x: $$\frac{d}{dx}[\ln(y)] = \frac{d}{dx}\left[x\ln\left(\frac{1}{x}\right)\right]$$ Recall that the derivative of $$\ln(y)$$ with respect to x is $$\frac{1}{y}\frac{dy}{dx}$$: $$\frac{1}{y}\frac{dy}{dx} = \frac{d}{dx}\left[x\ln\left(\frac{1}{x}\right)\right]$$
03

Apply the product rule to the right side of the equation

The right side of the equation has the product of two functions of x, so we need to apply the product rule. Let $$u = x$$ and $$v = \ln\left(\frac{1}{x}\right)$$. $$\frac{du}{dx} = 1$$ To find $$\frac{dv}{dx}$$,recall that the derivative of $$\ln(x)$$ is $$\frac{1}{x}$$ and apply the chain rule: $$\frac{dv}{dx} = \frac{d}{dx}[\ln(1/x)] = - \frac{1}{x^2}$$ Using the product rule, we get: $$\frac{dy}{dx}\Bigg|_{\frac{1}{y}} = \left(u\frac{dv}{dx} + v\frac{du}{dx}\right)$$ Substitute the values: $$\frac{1}{y}\frac{dy}{dx} = x\left(-\frac{1}{x^2}\right) + \ln\left(\frac{1}{x}\right)(1)$$
04

Solve for $$\frac{dy}{dx}$$

Multiply both sides of the equation by y: $$\frac{dy}{dx} = -\frac{y}{x} + y\ln\left(\frac{1}{x}\right)$$ Since $$y = \left(\frac{1}{x}\right)^{x}$$, substitute this expression back: $$\frac{dy}{dx} = -\frac{\left(\frac{1}{x}\right)^{x}}{x} + \left(\frac{1}{x}\right)^{x}\ln\left(\frac{1}{x}\right)$$ This is the derivative of the given function with respect to x.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Logarithmic Differentiation
Logarithmic differentiation is a technique used to simplify the differentiation process, especially when dealing with functions that involve products, quotients, or powers. This method is extremely helpful for complex exponents or when variables are present in both the base and the exponent, as seen in the function \( rac{1}{x})^{x}\).

To apply logarithmic differentiation, you take the natural logarithm of both sides of the equation, allowing you to work with sums instead of products or powers. For example, by letting \(y = (\frac{1}{x})^{x}\), and then taking the natural log of both sides, you get \(\ln(y) = x \ln(\frac{1}{x})\). This equation is much simpler to differentiate.

Logarithmic differentiation is powerful because it reduces the complexity of the original function, making it easier to apply other differentiation rules. Once differentiated, you can exponentiate to solve for the original function's derivative.
Implicit Differentiation
Implicit differentiation is a key technique used when you can't easily solve for one variable in terms of another. It's particularly useful when dealing with equations where one variable is defined implicitly by another variable, rather than explicitly.

In our solution, we implicitly differentiated \(\ln(y) = x \ln(\frac{1}{x})\) with respect to \(x\). Implicit differentiation allows us to find \(\frac{dy}{dx}\) without actually solving for \(y\). The derivative of \(\ln(y)\) is \(\frac{1}{y}\frac{dy}{dx}\), since \(y\) is a function of \(x\).

This approach requires keeping track of derivatives and using the chain rule appropriately, as you'll often find derivatives of nested functions.
Product Rule
The product rule is essential when differentiating a product of two functions. It states that the derivative of a product \(u(x) \cdot v(x)\) is \(u'v + uv'\). This is fundamental in many calculus problems.

In our problem, to differentiate \(x\ln(\frac{1}{x})\), we use this rule by letting \(u = x\) and \(v = \ln(\frac{1}{x})\). First, you find the derivatives: \(\frac{du}{dx} = 1\) and you use chain rule to get \(\frac{dv}{dx} = -\frac{1}{x^2}\).

Applying the product rule, the derivative becomes \(x(-\frac{1}{x^2}) + \ln(\frac{1}{x})(1)\). This method efficiently handles products of functions without excessive complexity.
Chain Rule
The chain rule is crucial when differentiating compositions of functions, i.e., when you have a function inside another function. It allows you to take the derivative of the outer function and multiply it by the derivative of the inner function.

When differentiating \(\ln(\frac{1}{x})\), the chain rule is applied. You first consider \(\frac{1}{x}\) as the inner function and \(\ln(x)\) as the outer function. The chain rule states that the derivative of \(\ln(u)\) with respect to \(x\) is \(\frac{1}{u} \cdot \frac{du}{dx}\). In this case, \(u = \frac{1}{x}\) so \(\frac{du}{dx} = -\frac{1}{x^2}\).

Therefore, the derivative becomes \(-\frac{1}{x}\), indicating how chain rule enables handling nested functions effectively.

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Most popular questions from this chapter

Use a calculator to evaluate each expression, or state that the value does not exist. Report answers accurate to four decimal places. a. \(\operatorname{coth} 4\) b. \(\tanh ^{-1} 2\) c. \(\operatorname{csch}^{-1} 5\) d. \(\left.\operatorname{csch} x\right|_{1 / 2} ^{2}\) e. \(\ln | \tanh (x / 2) \|_{1}^{10} \quad\) f. \(\left.\tan ^{-1}(\sinh x)\right|_{-3} ^{3} \quad\) g. \(\left.\frac{1}{4} \operatorname{coth}^{-1}\left(\frac{x}{4}\right)\right|_{20} ^{\frac{36}{6}}\)

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