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Use any method to evaluate the integrals. Most will require trigonometric substitutions, but some can be evaluated by other methods. \(\int \frac{v^{2} d v}{\left(1-v^{2}\right)^{5 / 2}}\)

Short Answer

Expert verified
\(\frac{v^3}{3(1-v^2)^{3/2}} + C\]."

Step by step solution

01

Identify the Appropriate Substitution

The integral contains the term \((1-v^2)^{5/2}\), which resembles \(\sqrt{1-v^2}\), a derivative linked to the trigonometric identity \(\sin^2 \theta + \cos^2 \theta = 1\), suggesting a trigonometric substitution. Use \(v = \sin \theta\), hence \(dv = \cos \theta \, d\theta\), and substitute into the integral. Also note, \(1-v^2 = \cos^2 \theta\).
02

Rewrite the Integral Using the Substitution

Substitute \(v = \sin \theta\) and \(dv = \cos \theta \, d\theta\) into the integral to get: \[\int \frac{(\sin \theta)^2 \cos \theta \, d\theta}{(\cos^2 \theta)^{5/2}} = \int \frac{\sin^2 \theta \cos \theta \, d\theta}{\cos^5 \theta}\].This simplifies to \[\int \frac{\sin^2 \theta}{\cos^4 \theta} \, d\theta\].Simplify further to \[\int \tan^2 \theta \, \sec^2 \theta \, d\theta\].
03

Simplify the Integral Using a Known Identity

Transform \(\tan^2 \theta\) using the identity \(\tan^2 \theta = \sec^2 \theta - 1\): \[\int (\sec^2 \theta - 1) \sec^2 \theta \, d\theta = \int (\sec^4 \theta - \sec^2 \theta) \, d\theta\].
04

Integrate Each Term Separately

Separate the integral into two integrals: \[\int \sec^4 \theta \, d\theta - \int \sec^2 \theta \, d\theta\].Recall standard integrals: \[\int \sec^2 \theta \, d\theta = \tan \theta + C\].The integral \(\int \sec^4 \theta \, d\theta\) involves integration by parts or known results, giving us:\[\int \sec^4 \theta \, d\theta = \frac{1}{3} \tan^3 \theta + \tan \theta + C_1\].
05

Combine the Results

Combine the results of the separate integrals: \[ \frac{1}{3} \tan^3 \theta + \tan \theta - \tan \theta + C\].Simplifying, we find \[ \frac{1}{3} \tan^3 \theta + C\].
06

Convert Back to Original Variable

Recall the substitution \(v = \sin \theta\), meaning \(\tan \theta = \frac{v}{\sqrt{1-v^2}}\). Substitute back to get: \[\frac{1}{3} \left(\frac{v}{\sqrt{1-v^2}}\right)^3 + C = \frac{v^3}{3(1-v^2)^{3/2}} + C\].

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Key Concepts

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

Integral Calculus
Integral calculus is an essential branch of mathematics that helps us evaluate the area under curves, among other applications. In this exercise, we are tasked with evaluating an integral by using trigonometric substitution. The process starts with identifying the structure of the integral. The expression \(\int \frac{v^2 \, dv}{(1-v^2)^{5/2}}\) contains the term that resembles \(\sqrt{1-v^2}\). This similarity suggests that a trigonometric identity might simplify the problem.

When dealing with expressions involving \(1 - v^2\), trigonometric substitution can effectively simplify calculations. The core idea is to replace the variable with a trigonometric function that has a known derivative. Through this substitution, the algebraic expression transforms into a trigonometric one, making the integral easier to evaluate.

For anyone learning integral calculus, understanding how to approach and manipulate integrals with trigonometric substitution is a crucial skill. By working through this exercise, one gains insight into simplifying complex expressions into tractable forms that are easier to integrate.
Trigonometric Identities
Trigonometric identities are equations that involve trigonometric functions and are always true for any angle. These identities serve as powerful tools in calculus, especially when transforming complex integrals. An important trigonometric identity used in this exercise is \(\sin^2 \theta + \cos^2 \theta = 1\), which is foundational for substituting variables and simplifying expressions.

In this particular problem, substituting \(v = \sin \theta\) transforms the troublesome expression \(1 - v^2\) into \(\cos^2 \theta\). The identity streamlines integration by making parts of the equation easier to handle, ultimately reducing the original integral into simpler components.

Another key trigonometric identity used was changing \(\tan^2 \theta\) into \(\sec^2 \theta - 1\). Such transformations provide a way to further simplify the integral, breaking it down into known integrals that can be solved with standard techniques.
  • Using identities simplifies the integral.
  • Converting terms with identities can lead to easier integrations.
Mastery of these identities can dramatically ease the process of solving demanding calculus problems.
Integration Techniques
Integration techniques serve as the toolkit for evaluating a wide array of integrals. When standard integration methods do not suffice, advanced techniques such as trigonometric substitution, integration by parts, and recognizing standard integral forms become invaluable.

In our exercise, trigonometric substitution was the primary technique. By using \(v = \sin \theta\), the integral is reshaped into a trigonometric integral. Once substitution is complete, simplifying the integral further by separating terms, as seen when the expression transforms to \(\int \tan^2 \theta \, \sec^2 \theta \, d\theta\), is beneficial. Next comes the application of identities and standard integral forms to separate and solve each component.

For achieving a clean result, all calculated integrals are integrated individually. In this case, \(\int \sec^4 \theta \, d\theta\) and \(\int \sec^2 \theta \, d\theta\) are tackled separately. Understanding these individual techniques, and how they interrelate, is crucial for handling complex calculus problems efficiently.
  • Integration techniques are applicable based on problem structure.
  • Combining techniques often provides the simplest solution.
Building proficiency in these methods expands one's ability to solve a diverse set of integrals with ease and confidence.

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Most popular questions from this chapter

Compare the results of using Equations (4) and (5). Equations (4) and (5) lead to different formulas for the integral of \(\tan ^{-1} x\) a. \(\int \tan ^{-1} x d x=x \tan ^{-1} x-\ln \sec \left(\tan ^{-1} x\right)+C\) Eq. (4) b. \(\int \tan ^{-1} x d x=x \tan ^{-1} x-\ln \sqrt{1+x^{2}}+C\) Eq. (5) Can both integrations be correct? Explain.

A manufacturer of generator shafts finds that it needs to add additional weight to its shafts in order to achieve proper static and dynamic balance. Based on experimental tests, the average weight it needs to add is \(\mu=35\) g with \(\sigma=9\) g. Assuming a normal distribution, from 1000 randomly selected shafts, how many would be expected to need an added weight in excess of 40 g?

a. Use a CAS to evaluate $$\int_{0}^{\pi / 2} \frac{\sin ^{n} x}{\sin ^{n} x+\cos ^{n} x} d x$$ where \(n\) is an arbitrary positive integer. Does your CAS find the result? b. In succession, find the integral when \(n=1,2,3,5,\) and 7 Comment on the complexity of the results. c. Now substitute \(x=(\pi / 2)-u\) and add the new and old integrals. What is the value of $$\int_{0}^{\pi / 2} \frac{\sin ^{n} x}{\sin ^{n} x+\cos ^{n} x} d x ?$$ This exercise illustrates how a little mathematical ingenuity solves a problem not immediately amenable to solution by a CAS.

Use integration, the Direct Comparison Test, or the limit Comparison Test to test the integrals for convergence. If more than one method applies, use whatever method you prefer. $$\int_{2}^{\infty} \frac{d x}{\sqrt{x^{2}-1}}$$

In a population of 500 adult Swedish males, medical researchers find their brain weights to be approximately normally distributed with mean \(\mu=1400 \mathrm{g}\) and standard deviation \(\sigma=100 \mathrm{g}\). a. What percentage of brain weights are between 1325 and 1450 g? b. How many males in the population would you expect to have a brain weight exceeding \(1480 \mathrm{g} ?\)

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