Calculating Volume by Rotating y = e^x * sin(x) Around the x-Axis

In summary, the conversation discusses finding the volume of a figure by rotating a function around the x-axis. The function is y = e^x * sin(x) and the integral to solve is pi * ∫e^(2x) * sin^2(x) dx. The conversation suggests changing sin squared into a more manageable form, such as 1/2 - (1/2)cos2x. This leads to solving two integrals, with the second one requiring integration by parts twice. Ultimately, this approach may help in solving the original integral.
  • #1
TSN79
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I'm supposed to find the volume of the figure that appears by rotating the follwing around the x-axis:
[tex]y = e^x \cdot \sin (x) & x \in \left[ {0,\left. \pi \right]} \right.[/tex]
This means (I think) that the function needs to be to the second power and multiplied by Pi in an integral. So the integral becomes
[tex]
\pi \int {e^{2x} \cdot \sin ^2 (x)dx}
[/tex]
I need hints on how to solve this integral, I've tried integration by parts but not really gotten anywhere...am I on the right track?
 
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  • #2
here is a hint, maybe change sin squared into something more friendly.
 
Last edited:
  • #3
I tried to change it into 1-cos2x = 2(sinx)^2, but I didn't find it to make it any easier...was that what you thought about?
 
  • #4
yes, change (sinx)^2 = 1/2 - (1/2)cos2x. multiply your e function through and you will have 2 integrals that can be solved. the integral with (e^2x)(1/2 cos 2x) is going to need parts twice.
 
Last edited:
  • #5
I do believe you might be on to something there 1800bigk...thx!
 

1. How do you calculate the volume of a shape rotated around the x-axis?

To calculate the volume of a shape rotated around the x-axis, you will need to use the formula V = π∫(f(x))^2 dx, where f(x) is the function representing the shape. In this case, the function is y = e^x * sin(x).

2. What is the process for finding the limits of integration for this problem?

The limits of integration for this problem can be found by setting the function equal to 0 and solving for x. In this case, e^x * sin(x) = 0 at x = 0 and x = π. Therefore, the limits of integration are 0 and π.

3. How do you set up the integral for this problem?

To set up the integral for this problem, you will need to plug in the limits of integration and the function into the formula V = π∫(f(x))^2 dx. In this case, the integral will be V = π∫(e^x * sin(x))^2 dx with limits of integration 0 and π.

4. Can this problem be solved using any other method besides integration?

No, this problem can only be solved using integration. This is because integration is the only method that allows us to find the volume of a shape that has been rotated around an axis.

5. How do you evaluate the integral for this problem?

To evaluate the integral for this problem, you can use techniques such as substitution or integration by parts. However, since this is a specific problem with given limits of integration, you can also use a calculator or software to find the numerical answer.

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