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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 4, Problem 4.7.45

Finding Indefinite Integrals


In Exercises 17–56, find the most general antiderivative or indefinite integral. You may need to try a solution and then adjust your guess. Check your answers by differentiation.


∫(sin2x − csc²x)dx

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1
Rewrite the integral by separating it into two simpler integrals: \(\int (\sin 2x - \csc^2 x) \, dx = \int \sin 2x \, dx - \int \csc^2 x \, dx\).
Recall the integral formulas for each term: the integral of \(\sin 2x\) and the integral of \(\csc^2 x\). Specifically, use the substitution method for \(\sin 2x\) and the known antiderivative for \(\csc^2 x\).
For \(\int \sin 2x \, dx\), let \(u = 2x\), so \(du = 2 \, dx\) or \(dx = \frac{du}{2}\). Rewrite the integral in terms of \(u\) and integrate.
For \(\int \csc^2 x \, dx\), recall that the derivative of \(\cot x\) is \(-\csc^2 x\), so the integral of \(\csc^2 x\) is \(-\cot x\) plus a constant.
Combine the results from both integrals and add the constant of integration \(C\) to write the most general antiderivative. Finally, verify your answer by differentiating it to check if you get the original integrand.

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Key Concepts

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

Indefinite Integral and Antiderivative

An indefinite integral represents the most general antiderivative of a function, including a constant of integration. It reverses differentiation, finding a function whose derivative matches the integrand. For example, ∫f(x)dx = F(x) + C, where F'(x) = f(x).
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Integration of Trigonometric Functions

Integrating trigonometric functions like sin(2x) and csc²(x) requires knowledge of standard integral formulas and substitution techniques. For instance, ∫sin(2x)dx can be solved using a substitution for the inner function, while ∫csc²(x)dx is a standard integral equal to -cot(x) + C.
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Verification by Differentiation

After finding an antiderivative, verifying the solution by differentiating it ensures correctness. Differentiation of the proposed integral should return the original integrand. This step confirms the integral was computed accurately and helps identify any errors.
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