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Ch. 5 - Integrals
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 5, Problem 5.PE.37

Evaluating Indefinite Integrals


Evaluate the integrals in Exercises 37–46.


∫ 2(cos x)⁻¹/² sin x dx

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1
Recognize that the integral is of the form \(\int 2 (\cos x)^{-\frac{1}{2}} \sin x \, dx\), which suggests a substitution involving \(\cos x\) because its derivative is related to \(\sin x\).
Let \(u = \cos x\). Then, compute the differential \(du = -\sin x \, dx\), which implies \(-du = \sin x \, dx\).
Rewrite the integral in terms of \(u\): substitute \(\cos x\) with \(u\) and \(\sin x \, dx\) with \(-du\), so the integral becomes \(\int 2 u^{-\frac{1}{2}} (-du)\).
Simplify the integral to \(-2 \int u^{-\frac{1}{2}} \, du\), which is a basic power integral.
Use the power rule for integration: \(\int u^{n} \, du = \frac{u^{n+1}}{n+1} + C\) for \(n \neq -1\), and apply it to \(u^{-\frac{1}{2}}\) to find the antiderivative.

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Key Concepts

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

Indefinite Integrals

An indefinite integral represents the family of all antiderivatives of a function and is expressed without limits of integration. It includes a constant of integration (C) because differentiation of a constant is zero. Understanding indefinite integrals is essential for reversing differentiation and finding original functions.
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Integration by Substitution

Integration by substitution is a method used to simplify integrals by changing variables. It involves identifying a part of the integrand as a new variable (u), rewriting the integral in terms of u, and then integrating. This technique is especially useful when the integral contains a function and its derivative.
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Trigonometric Functions and Their Integrals

Trigonometric functions like sine and cosine have specific integral formulas and properties. Recognizing how to manipulate powers and compositions of trig functions is crucial. For example, integrating expressions involving powers of cosine or sine often requires substitution or trigonometric identities.
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