Integral of hyperbolic function

In summary, the given expression can be simplified to \frac{1}{\sqrt 3} \ln \left[\frac {3\sqrt 3+5}{\sqrt{12}+\sqrt{10}}\right] or \frac{1}{\sqrt 3}\ln \left (\frac{15+\sqrt {219}}{12+\sqrt {138}}\right), but there seems to be a discrepancy between the two potential answers. It is possible that either the question or the answer is incorrect.
  • #1
DryRun
Gold Member
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Homework Statement
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx[/tex]

The attempt at a solution
I complete the square for the quadratic:
[tex]\sqrt{3x^2-6x+1}
\\=\sqrt{3(x^2-2x+\frac{1}{3})}
\\=\sqrt 3 \times \sqrt{(x-1)^2-\frac{2}{3}}[/tex]
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx
\\=\frac{1}{\sqrt 3}\int^4_3 \frac{1}{\sqrt{(x-1)^2-\frac{2}{3}}}\,.dx
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{\sqrt 3(x-1)}{\sqrt 2}\right]^{x=4}_{x=3}
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{3\sqrt 3}{\sqrt 2}-\cosh^{-1}\sqrt 6\right][/tex]
I already simplified it but it doesn't agree with the final answer:
[tex]\frac{1}{\sqrt 3}\ln \left(\frac{15+\sqrt {219}}{12+\sqrt {138}}\right)[/tex]
 
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  • #2
hi sharks! :smile:

cosh-1x = ln(ecosh-1x)

= ln(cosh(cosh-1x) + sinh(cosh-1x))

= ln (x + √(x2 - 1)) :wink:
 
  • #3
Hi tiny-tim :smile:

The above expression is what i used to expand:
[tex]\frac{1}{\sqrt 3} \left [\cosh^{-1}\frac{3\sqrt 3}{\sqrt 2}-\cosh^{-1}\sqrt 6\right]
\\=\frac{1}{\sqrt 3} \ln \left[\frac {3\sqrt 3+5}{\sqrt{12}+\sqrt{10}}\right]=0.4625025064[/tex]
But if i evaluate the answer from my notes, i get:
[tex]\frac{1}{\sqrt 3}\ln \left (\frac{15+\sqrt {219}}{12+\sqrt {138}}\right)=0.1310541888[/tex]
Since the answers are not the same, I'm thinking that maybe the answer in my notes is wrong?
 
Last edited:
  • #4
well that's obviously …
[tex]\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{\sqrt 3(x+1)}{\sqrt 2}\right]^{x=4}_{x=3}[/tex]

… either the question or the answer is wrong
 

What is the integral of a hyperbolic function?

The integral of a hyperbolic function is the inverse operation of differentiation. It is a mathematical technique used to find the original function when the derivative of that function is known.

What are some common hyperbolic functions?

Some common hyperbolic functions include sinh(x), cosh(x), tanh(x), sech(x), csch(x), and coth(x). These functions are related to exponential functions and have a similar shape to trigonometric functions.

How is the integral of a hyperbolic function different from the integral of a trigonometric function?

The main difference is in the algebraic expressions used to represent the functions. The integral of a hyperbolic function involves hyperbolic trigonometric identities, while the integral of a trigonometric function involves trigonometric identities. Additionally, the domain and range of hyperbolic functions are different from trigonometric functions.

What are some applications of hyperbolic functions in science?

Hyperbolic functions are used in a variety of scientific fields, such as physics, engineering, and economics. They can be used to model the behavior of springs, describe the shape of a hanging cable, and analyze population growth. They also have applications in signal processing and control systems.

How do you solve an integral of a hyperbolic function?

The process for solving an integral of a hyperbolic function involves using integration techniques such as substitution, integration by parts, or partial fractions. It is also helpful to have a solid understanding of hyperbolic trigonometric identities and their derivatives. Practice and familiarity with these techniques will make solving integrals of hyperbolic functions easier.

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