Chapter 7: Problem 56
(a) Make an appropriate \(u\) -substitution of the form \(u=x^{1 / n}\) or \(u=(x+a)^{1 / n},\) and then evaluate the integral. (b) If you have a CAS, use it to evaluate the integral, and then confirm that the result is equivalent to the one that you found in part (a). $$\int \frac{1}{x \sqrt{x^{3}-1}} d x$$
Short Answer
Step by step solution
Choose the Substitution
Differentiate and Solve for dx
Express x and the Integral in Terms of u
Simplify the Integral
Solve the Integral
Convert the Result Back to x
Verify with CAS
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integral Calculus
In this particular exercise, the integral to evaluate is \( \int \frac{1}{x \sqrt{x^{3}-1}} dx \). This integral is complex due to the presence of \( x \) both in the denominator and within the square root. To tackle this, a smart substitution method is employed.
The key concept in integral calculus used here is identifying forms that can be simplified using a suitable transformation. This involves recognizing patterns where substitution can help rewrite the integral into something easier to evaluate. Here, the complexity lies in simplifying the expression \( \sqrt{x^3-1} \), aiming to turn a challenging integral into one that is manageable.
Substitution Method
In the given problem, the substitution \( u = x^{1/3} \) is used. This choice effectively handles the root expression \( \sqrt{x^3 - 1} \).
- The differentiation \( \frac{du}{dx} = \frac{1}{3}x^{-2/3} \) helps express \( dx \) in terms of \( du \).
- This leads to \( dx = 3u^2 \, du \), simplifying the entire expression into the variable \( u \).
Calculus Verification
Using a CAS, or Computer Algebra System, is an effective way to verify calculus solutions. CAS tools can solve integrals, differentiate, and perform many other calculus operations.
In this exercise, after performing u-substitution and manual integration, we're encouraged to use CAS to verify the result. The CAS confirms that the integral of \( \int \frac{1}{x \sqrt{x^3 - 1}} \, dx \) results in \( 2 \ln \left| \sqrt{x^3 - 1} + x \right| + C \). This verification step is crucial as it cross-checks our manual solution against a system, ensuring that the analogical solution aligns with computational outputs.