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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. $$\begin{array}{l}{\int \cot ^{2} x d x} \\ {\left(\operatorname{Hint} : 1+\cot ^{2} x=\csc ^{2} x\right)}\end{array}$$

Short Answer

Expert verified
The general antiderivative is \(-\cot x - x + C\).

Step by step solution

01

Use the Trigonometric Identity

We know from the hint that \(1+\cot^2 x=\csc^2 x\). We can rewrite \(\cot^2 x\) in terms of \(\csc^2 x\) using the identity: \(\cot^2 x = \csc^2 x - 1\).
02

Substitute in the Integral

Substitute \(\cot^2 x\) with \(\csc^2 x - 1\) in the original integral to get: \[\int \cot^2 x \, dx = \int (\csc^2 x - 1) \, dx.\]
03

Split the Integral

Split the integral into two separate integrals: \[\int (\csc^2 x - 1) \, dx = \int \csc^2 x \, dx - \int 1 \, dx.\]
04

Integrate Each Term

Integrate each term separately: - The integral of \(\csc^2 x\) is \(-\cot x\). - The integral of \(1\) is simply \(x\). Hence,\[\int \csc^2 x \, dx = -\cot x\] and\[\int 1 \, dx = x.\]
05

Combine Results with a Constant of Integration

Combine the results from each integral:\[\int \cot^2 x \, dx = -\cot x - x + C,\]where \(C\) is the constant of integration.
06

Differentiate to Check the Solution

Differentiate the result \(-\cot x - x + C\) to verify the solution:\[-\frac{d}{dx}(\cot x) = \csc^2 x,\]\[-\frac{d}{dx}(x) = 1.\]Thus, the derivative of \(-\cot x - x + C\) is \(\csc^2 x - 1 = \cot^2 x\), confirming that our anti-derivative was correct.

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Key Concepts

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

Antiderivative
When we talk about the antiderivative, we're focusing on finding a function whose derivative gives us the original function. It's akin to reversing differentiation. In this particular problem, our task is to find the most general antiderivative of the function \(\cot^2 x\), which means looking for a function that, when differentiated, results in \(\cot^2 x\).

Antiderivatives are a fundamental part of calculus because they help us compute areas, solve differential equations, and model physical systems. One way to find an antiderivative is by checking if we can rewrite the function in a form easier to integrate, often using trigonometric identities or simplification techniques. After rewriting, we perform the integration and add a constant of integration, \(C\), since the differentiation of a constant is zero.

Using techniques like substitution is key. In this problem, aiming for \(\int \cot^2 x \, dx\), we managed to rewrite \(\cot^2 x\) using the identity \(\csc^2 x - 1\), making it straightforward to integrate.
Trigonometric Identities
Trigonometric identities are equations that involve trigonometric functions and are true for every value of the occurring variables. They are essential in simplifying trigonometric expressions, solving equations, and finding integrals or derivatives.

In the exercise, we use the identity \(1 + \cot^2 x = \csc^2 x\). This identity comes from the Pythagorean trigonometric identities, which are fundamental in calculus operations involving trigonometric functions. By rearranging it to \(\cot^2 x = \csc^2 x - 1\), we considerably simplify the task at hand.

Utilizing such identities:
  • Provides a pathway to simplify complex integrals or equations.
  • Aids the transformation of expressions into more manageable forms, allowing for easier computation of antiderivatives.
  • Is essential in both integrating functions and proofreading by differentiation.
Integration Techniques
Integration techniques are a set of methods used to find integrals, whether definite or indefinite. These techniques often involve recognizing patterns or substituting variables to make integration more manageable.

Here are a few common techniques:
  • Substitution: Changing variables to simplify the integral. For example, using trigonometric identities as in this problem.
  • Partial Fractions: Decomposing a fraction into simpler parts for integration.
  • Integration by Parts: Integrating products of functions by relegating part of the integral to differentiation.
In this exercise, we employed substitution by substituting \(\cot^2 x\) for \(\csc^2 x - 1\), then split the integral into separate, simpler integrals \(\int \csc^2 x \, dx\) and \(\int 1 \, dx\).

This approach was straightforward:
  • The integral of \(\csc^2 x\) yields \(-\cot x\).
  • The integral of a constant \(1\) simply results in \(x\).
Combining these results correctly and adding a constant \(C\) forms the solution to the indefinite integral. By differentiating the outcome, we confirm its validity, ensuring we reach \(\cot^2 x\) when the solution is differentiated, which verifies our integration process.

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