Triple Integral: Having trouble finding my y bounds

In summary, the given conversation discusses a problem involving a triple integral of a function over a bounded region E, which is defined by a parabolic cylinder and several planes. The speaker notes that the graph of the parabolic cylinder has symmetry and stretches infinitely along the x-axis. After receiving a hint, it is mentioned that the solution is relatively straightforward, with the region being projected onto the xy-plane and the integrals taken over specific bounds.
  • #1
Saladsamurai
3,020
7

Homework Statement



[tex]I=\int\int\int_E x^2e^ydV[/tex] where E is bounded by the parabolic cylinder

z=1-y^2 and the planes z=0 x=1 and x=-1

I know that the graph is a parabola that opens downwards and that has symmetry wrt the x-axis. It also stretches along the x-axis toward + and - infinity.

Can I get a hint here? :)
 
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  • #2
Did you mean
[tex]I=\int\int\int_E x^2e^y\,dV[/tex] ?
 
  • #3
It's pretty close to being trivial. The parabola z= 1- y2 has z= 0 at y= -1 and y= 1 so projecting down on to xy=plane, we get the square -1< x< 1, -1< y< 1. The z- integral is taken from 0 to 1- y2, the y integral from -1 to 1, and the x integral from -1 to 1.
 
  • #4
Avodyne said:
Did you mean
[tex]I=\int\int\int_E x^2e^y\,dV[/tex] ?

I don't see any difference. So yes. :smile:
 

1. What is a triple integral?

A triple integral is a mathematical tool used to calculate the volume of a three-dimensional object or the mass of a three-dimensional shape with varying density.

2. How is a triple integral different from a regular integral?

A regular integral is used to find the area under a curve, while a triple integral is used to find the volume of a three-dimensional shape.

3. What are the variables in a triple integral?

A triple integral has three variables: x, y, and z, which represent the three dimensions of the object being calculated.

4. How do I determine the bounds for the y variable in a triple integral?

The bounds for the y variable depend on the shape of the object and the limits of integration for the x and z variables. You can determine the bounds by visualizing the object and determining the range of y values that make up its volume.

5. What should I do if I am having trouble finding the y bounds in a triple integral?

If you are having trouble finding the y bounds, you can try visualizing the object or breaking it down into simpler shapes that have known volume formulas. You can also consult with a math tutor or a fellow scientist for assistance.

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