How Do You Solve This Integral with \( e \) in the Denominator?

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In summary, the conversation discussed solving the integral $$\int_{}^{} \frac{1}{e^x + e^{-x}}\,dx$$ by first multiplying the integrand by $\frac{e^x}{e^x}$ and then using the substitution $u = e^x$. It was then suggested to proceed either by recognizing this as a well-known integral or by using a trigonometric substitution.
  • #1
tmt1
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How can I go about solving this problem?

$$\int_{}^{} \frac{1}{e^x + e^{-x}}\,dx$$

I am unsure how to start.
 
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  • #2
I would begin by multiplying the integrand by:

\(\displaystyle 1=\frac{e^x}{e^x}\)

and then use the substitution:

\(\displaystyle u=e^x\)

Can you proceed?
 
  • #3
MarkFL said:
I would begin by multiplying the integrand by:

\(\displaystyle 1=\frac{e^x}{e^x}\)

and then use the substitution:

\(\displaystyle u=e^x\)

Can you proceed?

so I would get

$$\int_{}^{} \frac{e^x}{2} \,dx$$

Then $e^x = u$ so $du = e^x dx$. Then I can substitute that and get

$$\frac{1}{2} \int_{}^{} \,du$$

Or $\frac{1}{2} u + C$ which becomes $\frac{1}{2} e^x + C$. Is this right?
 
  • #4
tmt said:
so I would get

$$\int_{}^{} \frac{e^x}{2} \,dx$$

Then $e^x = u$ so $du = e^x dx$. Then I can substitute that and get

$$\frac{1}{2} \int_{}^{} \,du$$

Or $\frac{1}{2} u + C$ which becomes $\frac{1}{2} e^x + C$. Is this right?

No, let's begin with the original:

\(\displaystyle I=\int\frac{1}{e^x+e^{-x}}\,dx\)

Now, using my first suggestion, we obtain:

\(\displaystyle I=\int\frac{1}{e^x+e^{-x}}\cdot\frac{e^x}{e^x}\,dx=\int\frac{e^x}{\left(e^x\right)^2+1}\,dx\)

Then, using my second suggestion:

\(\displaystyle u=e^x\implies du=e^x\,dx\)

we now have:

\(\displaystyle I=\int\frac{1}{u^2+1}\,du\)

Now you can proceed either by recognizing this is a well-known integral, or use a trigonometric substitution. :)
 
  • #5
tmt said:
$$\int \frac{dx}{e^x + e^{-x}}$$

Careful!

MarkFL's advice goes like this:

$$\int \frac{e^x}{e^x}\cdot\frac{1}{e^x + e^{-x}}\,dx \;=\;\int \frac{e^x}{e^{2x} + 1}\,dx \;=\;\int \frac{e^x}{(e^x)^2 + 1}\,dx $$

$$\text{Let }u = e^x \quad\Rightarrow\quad du = e^x\,dx $$

$$\text{Substituite: }\;\int \frac{du}{u^2+1} $$

$\text{Got it?}$
 

FAQ: How Do You Solve This Integral with \( e \) in the Denominator?

1. What is an Integral with e in the denominator?

An integral with e in the denominator is a type of mathematical expression that involves the constant "e" (Euler's number) in the denominator of the integrand. It is commonly used in calculus and can represent a wide range of functions.

2. How do you solve an Integral with e in the denominator?

To solve an integral with e in the denominator, you can use integration techniques such as u-substitution or integration by parts. It is important to have a good understanding of calculus and integration rules to properly solve these types of integrals.

3. What are the applications of Integrals with e in the denominator?

Integrals with e in the denominator have various applications in physics, engineering, and economics. In physics, they can represent the decay of radioactive substances. In engineering, they can model the behavior of electric circuits. In economics, they can be used to calculate compound interest.

4. Are there any special properties of Integrals with e in the denominator?

Yes, there are some special properties of integrals with e in the denominator. One important property is that the integral of e to the power of x is equal to e to the power of x plus a constant. This property is often used when solving integrals with e in the denominator.

5. Can you provide an example of an Integral with e in the denominator?

Sure, an example of an integral with e in the denominator is ∫(e^x)/x dx. This integral can be solved using the integration by parts technique, and the result is e^x plus a constant. In this example, the constant is necessary because the derivative of x is 1, which is not present in the original integrand.

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