/*! 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 31 Find the integrals. $$\int x \... [FREE SOLUTION] | 91Ó°ÊÓ

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Find the integrals. $$\int x \sinh x \, d x$$

Short Answer

Expert verified
\( \int x \sinh x \, dx = x \cosh x - \sinh x + C \)

Step by step solution

01

Choose the Integration Technique

To solve the integral \( \int x \sinh x \, dx \), we need to use the technique of integration by parts. Integration by parts is usually applied when the integral is a product of two functions. The formula for integration by parts is:\[\int u \, dv = u v - \int v \, du\]We will choose \( u = x \) and \( dv = \sinh x \, dx \).
02

Differentiate and Integrate Parts

With \( u = x \), differentiate to find \( du \):\[ du = dx \]For \( dv = \sinh x \, dx \), integrate to find \( v \):\[ v = \cosh x \]This is because the derivative of \( \cosh x \) is \( \sinh x \).
03

Apply Integration by Parts Formula

Substitute \( u \), \( dv \), \( du \), and \( v \) into the integration by parts formula:\[\int x \sinh x \, dx = x \cosh x - \int \cosh x \, dx\]Now, we need to solve the remaining integral \( \int \cosh x \, dx \).
04

Integrate Remaining Integral

The integral \( \int \cosh x \, dx \) is straightforward:\[\int \cosh x \, dx = \sinh x + C\]where \( C \) is the constant of integration.
05

Assemble the Final Solution

Substitute the result from Step 4 back into the equation from Step 3:\[\int x \sinh x \, dx = x \cosh x - ( \sinh x + C )\]Simplify the expression to:\[\int x \sinh x \, dx = x \cosh x - \sinh x + C\]Thus, the integral of \( x \sinh x \) is \( x \cosh x - \sinh x + C \).

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Key Concepts

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

Hyperbolic Functions
When exploring integration problems, you might come across hyperbolic functions like \( \sinh x \) and \( \cosh x \). These functions are analogs to the trigonometric sine and cosine functions, but they are based on the exponential function. They're defined as follows:
  • \( \sinh x = \frac{e^x - e^{-x}}{2} \)
  • \( \cosh x = \frac{e^x + e^{-x}}{2} \)
Hyperbolic functions exhibit unique properties that are particularly useful in calculus:
  • The derivative of \( \sinh x \) is \( \cosh x \).
  • The derivative of \( \cosh x \) is \( \sinh x \).
Because of these properties, understanding hyperbolic functions is critical when solving integrals involving them. Knowing their derivatives can simplify integration processes, as demonstrated in the original exercise of finding \( \int x \sinh x \, dx \). By recognizing that \( \sinh x \) and \( \cosh x \) are related through differentiation, the problem becomes more approachable.
Indefinite Integrals
Indefinite integrals, also known as antiderivatives, represent a family of functions whose derivative is the original function given inside the integral. They typically include a constant of integration, \( C \), because differentiation of a constant results in zero, making it untraceable during integration.In the exercise provided, the task was to solve \( \int x \sinh x \, dx \). This problem involves finding an indefinite integral, which means solving for a general expression without specific bounds. The result of an indefinite integral provides all possible antiderivatives by incorporating \( + C \).Understanding indefinite integrals is crucial because:
  • They help understand the accumulation of quantities.
  • They provide the basis for solving differential equations.
  • They allow determination of area under curves in calculus problems.
Indefinite integrals capture the essence of a function's behavior and its potential transformations, integrating elements of algebra, geometry, and calculus.
Calculus Problem Solving
Calculus problem solving often involves various strategies and techniques to tackle intricate problems. Among these techniques, integration by parts is especially valuable when dealing with the product of two functions, as seen in the problem \( \int x \sinh x \, dx \).Integration by parts relies on the formula:\[ \int u \, dv = u v - \int v \, du \]The goal is to simplify the integral into forms that are more easily dealt with. The steps include:
  • Choosing a function to differentiate (\( u \)) and another to integrate (\( dv \)).
  • Differentiating \( u \) to find \( du \) and integrating \( dv \) to find \( v \).
  • Substituting these into the integration by parts formula.
This method not only helps solve complex integrals but also enhances understanding of calculus by reinforcing the connections between differentiation and integration. By effectively using integration by parts, you can deconstruct challenging calculus problems into manageable pieces, paving the way to finding elegant solutions. Exploring integration techniques like integration by parts provides foundational skills in problem-solving and mathematical analysis.

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Most popular questions from this chapter

Which technique is useful in evaluating the integral? (a) Integration by parts (b) Partial fractions (c) Long division (d) Completing the square (e) \(\quad\) A trig substitution (f) Other substitutions $$\int \frac{x^{2}}{1-x^{2}} d x$$

Decide whether the statements are true or false. Give an explanation for your answer. $$\int f^{\prime}(x) \cos (f(x)) d x=\sin (f(x))+C$$

Let \(f(t)\) be the rate of flow, in cubic meters per hour, of a flooding river at time \(t\) in hours. Give an integral for the total flow of the river (a) Over the 3 -day period \(0 \leq t \leq 72\). (b) In terms of time \(T\) in days over the same 3 -day period.

Find constants \(a, b, \lambda\) so that the integral has the form found in some tables of integrals: \(^{4}.\) $$\int \frac{e^{2 \lambda x}}{a e^{\lambda x}+b} d x$$ $$\int \frac{e^{6 x}}{4+e^{3 x+1}} d x$$

The rate at which water is flowing into a tank is \(r(t)\) gallons/minute, with \(t\) in minutes. (a) Write an expression approximating the amount of water entering the tank during the interval from time \(t\) to time \(t+\Delta t,\) where \(\Delta t\) is small. (b) Write a Riemann sum approximating the total amount of water entering the tank between \(t=0\) and \(t=5 .\) Write an exact expression for this amount. (c) By how much has the amount of water in the tank changed between \(t=0\) and \(t=5\) if \(r(t)=\) \(20 e^{0.02 t} ?\) (d) If \(r(t)\) is as in part (c), and if the tank contains 3000 gallons initially, find a formula for \(Q(t),\) the amount of water in the tank at time \(t\)

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