How Do You Integrate 1/√(x^3 + x^2 + x + 1) dx?

In summary: The book you're thinking of is Calculus: A Differentiable Approach, Third Edition, by James Stewart and Thomas H. Malthouse.
  • #1
askor
169
9
How do you integrate ##\frac{1}{\sqrt{x^3 + x^2 + x + 1}} \, dx##?

Please give me some hints and clues.

Thank you
 
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  • #2
I would write the polynomial as ##(x^2+1)(x+1)## and try a suitable substitution like ##x^2+1=u## or similar.
 
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  • #3
Do you have specific bounds to integrate between? Wolfram alpha suggests the answer to this is you do not.
 
  • #4
Elliptic integrals!
 
  • #5
For
[tex]x^3+x^2+x+1 \ge 0[/tex]
[tex]x \ge -1[/tex]
You should take care of integral interval for finite and real result.
 
  • #6
askor said:
How do you integrate ##\frac{1}{\sqrt{x^3 + x^2 + x + 1}} \, dx##?

Please give me some hints and clues.
It's a pretty interesting subject, elliptic integrals and functions if you're into that sort of thing. Check Wikipedia article: Elliptic integrals

. . . , with the appropriate reduction formula, every elliptic integral can be brought into a form that involves integrals over rational functions and the three Legendre canonical forms (i.e. the elliptic integrals of the first, second and third kind).

So it looks like you can express your integand as rational functions and the first, second, and third elliptical integrals and compute them using arithemetic-geometric means as per the reference. Sounds like an interesting research project but looks like it would take a bit of effort.
 
  • #7
So, it's an advance integration that did not taught in standard Calculus textbook, am I right?

May I know what book that teach an integration like this?
 
  • #8
What about this?

$$\int \frac{1}{\sqrt{x^3 + 6x^2 + 11x + 6}} \, dx$$

How do you integrate above?

Please give me a clues and hints.
 
  • #9

1. What is the process for integrating 1/√(x^3 + x^2 + x + 1) dx?

The process for integrating 1/√(x^3 + x^2 + x + 1) dx is to first simplify the expression by factoring out x^2 from the denominator, resulting in 1/√(x^2(x + 1) + 1). Then, use the substitution method by letting u = x + 1 and du = dx to rewrite the expression as 1/√(x^2u + 1). Finally, use the trigonometric substitution u = tanθ and du = sec^2θ dθ to solve the integral.

2. Can the integral 1/√(x^3 + x^2 + x + 1) dx be solved without using substitution?

No, the integral 1/√(x^3 + x^2 + x + 1) dx cannot be solved without using substitution. This is because the expression cannot be simplified or solved using any of the basic integration rules, such as power rule or u-substitution, and therefore requires the use of more advanced techniques like substitution.

3. What is the purpose of using substitution in solving the integral 1/√(x^3 + x^2 + x + 1) dx?

The purpose of using substitution in solving the integral 1/√(x^3 + x^2 + x + 1) dx is to simplify the expression and make it easier to solve. By substituting a new variable, u, for the expression in the denominator, the integral can be rewritten in terms of u, which can then be solved using trigonometric substitution.

4. Are there any special cases or exceptions when solving the integral 1/√(x^3 + x^2 + x + 1) dx?

Yes, there is one special case when solving the integral 1/√(x^3 + x^2 + x + 1) dx. When u = 0, the integral becomes undefined as it results in division by 0. To avoid this, the limits of integration must be adjusted to exclude u = 0.

5. Can the integral 1/√(x^3 + x^2 + x + 1) dx be solved using any other integration techniques?

No, the integral 1/√(x^3 + x^2 + x + 1) dx can only be solved using substitution and trigonometric substitution. Other integration techniques, such as integration by parts or partial fractions, cannot be applied to this integral.

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