/*! 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 65 Find \(d y / d x\) by implicit d... [FREE SOLUTION] | 91Ó°ÊÓ

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Find \(d y / d x\) by implicit differentiation. $$ x^{3}+x \tan ^{-1} y=e^{y} $$

Short Answer

Expert verified
\(\frac{dy}{dx} = \frac{-3x^2 - \tan^{-1}(y)}{\frac{x}{1+y^2} - e^y}\)

Step by step solution

01

Differentiate Both Sides with Respect to x

Differentiate the equation \(x^3 + x \tan^{-1}(y) = e^y\) with respect to \(x\), applying the derivative rules. On the left side, use the product rule for \(x \tan^{-1}(y)\) and on the right side, differentiate \(e^y\) by recognizing \(y\) as a function of \(x\).
02

Apply the Derivative to Each Term

The derivative of \(x^3\) is \(3x^2\). For \(x \tan^{-1}(y)\), use the product rule: it's \(\frac{d}{dx}\left[x \tan^{-1}(y)\right] = 1 \cdot \tan^{-1}(y) + x \cdot \frac{d}{dx}\left[\tan^{-1}(y)\right]\). Since \(\tan^{-1}(y)\) involves \(y\), apply the chain rule: the derivative is \(\frac{1}{1+y^2} \cdot \frac{dy}{dx}\). The derivative of \(e^y\) is \(e^y \cdot \frac{dy}{dx}\).
03

Form the Derivative Equation

Combine the derivatives: \(3x^2 + \tan^{-1}(y) + \frac{x}{1+y^2} \cdot \frac{dy}{dx} = e^y \cdot \frac{dy}{dx}\). This equation represents the derivative of the given equation with respect to \(x\).
04

Solve for dy/dx

Regroup the terms to have all \(\frac{dy}{dx}\) terms on one side: \(\frac{x}{1+y^2} \cdot \frac{dy}{dx} - e^y \cdot \frac{dy}{dx} = - 3x^2 - \tan^{-1}(y)\). Factor out \(\frac{dy}{dx}\): \(\frac{dy}{dx} \left( \frac{x}{1+y^2} - e^y \right) = -3x^2 - \tan^{-1}(y)\).
05

Isolate dy/dx

Divide both sides by \(\left( \frac{x}{1+y^2} - e^y \right)\) to solve for \(\frac{dy}{dx}\): \[ \frac{dy}{dx} = \frac{-3x^2 - \tan^{-1}(y)}{\frac{x}{1+y^2} - e^y} \]. This is the derivative of \(y\) with respect to \(x\) for the given equation.

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Key Concepts

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

Chain Rule
The Chain Rule is a fundamental tool in calculus used for differentiating composite functions. It allows us to find the derivative of a function with respect to a variable, even if that function is expressed in terms of another variable. In this exercise, the Chain Rule was essential for handling the term \(\tan^{-1}(y)\). This term involves \(y\), which is a function of \(x\), creating a situation where we need the Chain Rule.
  • The Chain Rule states that if you have a composite function \(f(g(x))\), then its derivative is \(f'(g(x)) \cdot g'(x)\).
  • When differentiating \(\tan^{-1}(y)\), we see \(y\) as an inner function dependent on \(x\). Hence, we apply the Chain Rule, finding first the derivative of \(\tan^{-1}(y)\) with respect to \(y\), resulting in \(\frac{1}{1+y^2}\), and then multiply by \(\frac{dy}{dx}\).
  • This enables us to relate changes in \(y\) to changes in \(x\), maintaining the relationship the original equation set forth.
Understanding and correctly applying the Chain Rule is key in dealing with implicit differentiation problems, particularly those involving inverse trigonometric functions like \(\tan^{-1}(y)\).
This ensures that all aspects of the dependency of \(y\) on \(x\) are accounted for in the derivative calculation.
Product Rule
In calculus, the Product Rule is vital for differentiating products of two or more functions. It helps us precisely determine the derivative when one function multiplies another. This becomes essential when terms in equations, such as \(x \tan^{-1}(y)\) in the exercise, involve the product of functions, where each component is dependent on the variable being differentiated.
  • The Product Rule states: if you have two functions, \(u(x)\) and \(v(x)\), then the derivative of their product is given by \(u'(x)v(x) + u(x)v'(x)\).
  • Using this rule on \(x \tan^{-1}(y)\), we first differentiate \(x\), resulting in \(1\), and multiply by \(\tan^{-1}(y)\).
  • Next, we keep \(x\) unchanged and differentiate \(\tan^{-1}(y)\), employing the Chain Rule as \(\frac{1}{1+y^2} \cdot \frac{dy}{dx}\), then add the results.
  • This step helps build the complete derivative necessary when differentiating the left side of the given equation.
Effectively applying the Product Rule simplifies complex expressions involving multiplied functions, aiding seamless navigation through implicit differentiation.
Derivatives
Derivatives are the cornerstone of calculus, allowing us to determine the rate of change of one variable with respect to another. In the context of this exercise, derivatives help us to find \(\frac{dy}{dx}\) using implicit differentiation.
  • The derivative of a function represents its rate of change and is denoted by \(\frac{d}{dx}\) or as \(f'(x)\).
  • Implicit differentiation is used when \(y\), an implicit function of \(x\), is not isolated or directly solvable. Here, treating \(y\) as an implicit function allows differentiation across both sides of equations.
  • In this problem, terms such as \(x^3\), \(x \tan^{-1}(y)\), and \(e^y\) are differentiated with respect to \(x\). The derivatives of these terms are calculated using appropriate rules like the Power Rule, Product Rule, and Chain Rule where necessary.
Understanding the concept of derivatives, including its various rules, empowers solving complex problems like the one shown, where composite and implicit functions are differentiated to find \(\frac{dy}{dx}\).
The methodical application of derivatives within this framework clarifies how variables interact and change together, providing deeper insight into implicit relationships.

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Most popular questions from this chapter

The side of a cube is measured to be \(25 \mathrm{~cm}\), with a possible error of \(\pm 1 \mathrm{~cm}\). (a) Use differentials to estimate the error in the calculated volume. (b) Estimate the percentage errors in the side and volume.

The electrical resistance \(R\) of a certain wire is given by \(R=k / r^{2}\), where \(k\) is a constant and \(r\) is the radius of the wire. Assuming that the radius \(r\) has a possible error of \(\pm 5 \%\), use differentials to estimate the percentage error in \(R\). (Assume \(k\) is exact.)

Verify that \(L\) 'Hôpital's rule is of no help in finding the limit; then find the limit, if it exists, by some other method. $$ \lim _{x \rightarrow+\infty} \frac{x(2+\sin 2 x)}{x+1} $$

Make a conjecture about the limit by graphing the function involved with a graphing utility; then check your conjecture using L'Hôpital's rule. $$ \lim _{x \rightarrow(\pi / 2)-} \frac{4 \tan x}{1+\sec x} $$

(a) Use a CAS to show that if \(k\) is a positive constant, then $$ \lim _{x \rightarrow+\infty} x\left(k^{1 / x}-1\right)=\ln k $$ (b) Confirm this result using \(\mathrm{L}\) 'Hôpital's rule. [Hint: Express the limit in terms of \(t=1 / x .]\) (c) If \(n\) is a positive integer, then it follows from part (a) with \(x=n\) that the approximation $$ n(\sqrt[n]{k}-1) \approx \ln k $$ should be good when \(n\) is large. Use this result and the square root key on a calculator to approximate the values of \(\ln 0.3\) and \(\ln 2\) with \(n=1024\), then compare the values obtained with values of the logarithms generated directly from the calculator. [Hint: The \(n\) th roots for which \(n\) is a power of 2 can be obtained as successive square roots.]

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