Need a little help starting this integral

  • Thread starter silverdiesel
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    Integral
In summary, the integral of 1/(e^x+1) can be solved using the substitution method with u = 1+e^-x, which results in the solution -ln(1+e^-x). This method can help build confidence in the integration process.
  • #1
silverdiesel
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[tex]\int\frac{1}{e^x+1}dx[/tex]

I have tried substitution, partial fraction decomposition, and integration by parts but I can't seem to figure it out. Any help is much appriciated. o:)
 
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  • #2
Hint: multiply top and bottom by [tex] e^{-x} [/tex].
 
  • #3
okay, then I can use u sub, which nets...

[tex]-ln (1+e^{-x})[/tex]

is that right?
 
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  • #4
That does not seem right. What I have I done wrong?

[tex]\int\frac{e^{-x}}{1+e^{-x}}dx[/tex]

[tex]u = 1+e^{-x}\\-du = e^{-x}[/tex]

[tex]-\int\frac{1}{u}du[/tex]
 
Last edited:
  • #5
silverdiesel said:
That does not seem right. What I have I done wrong?

[tex]\int\frac{e^{-x}}{1+e^{-x}}dx[/tex]

[tex]u = 1+e^{-x}\\-du = e^{-x}[/tex]

[tex]-\int\frac{1}{u}du[/tex]

It looks right to me, why do you think it's wrong?
 
  • #6
After further review, I don't think its wrong. I guess I am just working on building confidence in the integration process and I was hoping for some confirmation that is was done right. Thank you. These forums have been extremely helpful and I really appreciate all the quick and intelligent responces.
 

What is an integral?

An integral is a mathematical concept that represents the area under a curve on a graph. It is used to calculate the total amount of something, such as the total distance traveled by a moving object or the total volume of a 3-dimensional shape.

Why do we need to use integrals?

Integrals are useful in many areas of science and engineering. They allow us to find exact values for quantities that would otherwise be difficult or impossible to calculate. They are particularly important in areas such as physics, where they are used to calculate quantities like work, energy, and distance traveled.

How do I solve an integral?

Solving an integral involves finding the antiderivative of a function. This means finding a function that, when differentiated, gives the original function. There are several techniques for solving integrals, including integration by substitution, integration by parts, and integration using trigonometric identities.

What are the limits of integration?

The limits of integration specify the range of values over which the integral is evaluated. They are typically represented by numbers or variables and are written as part of the integral symbol. For definite integrals, the limits are necessary to find the exact value of the integral. For indefinite integrals, the limits are not needed.

Can integrals be used to solve real-world problems?

Yes, integrals are used in many real-world applications, such as calculating the area under a velocity-time graph to determine the total distance traveled by a moving object. They are also used in economics, engineering, and other areas of science to find exact values for quantities that are difficult to measure directly.

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