Determining double integral limits

In summary, the conversation discusses evaluating a surface integral over a circular cylinder in the xy plane with a given vector and determining the integration limits for the xz plane projection. However, there appears to be confusion about the problem statement and its lack of information about the height of the cylinder.
  • #1
JasonHathaway
115
0

Homework Statement



Evaluate [itex] \iint\limits_S \vec{A} . \vec{n} ds[/itex] over the plane [itex] x^{2}+y^{2}=16[/itex], where [itex]\vec{A}=z\vec{i}+x\vec{j}-3y^{2}\vec{k} [/itex] and S is a part from the plane and R was projected over xz-plane.

Homework Equations



Surface Integral and Double Integration.

The Attempt at a Solution



This is an answered problem, but I didn't get how to determine the integration limits

I understand that I have to integrate with respect to x and z due the fact the region is projected over "xz-plane", and I've to get the limits from the plane equation.

The limits integration in the solution are [itex] \int_0^5 \int_0^4 dz dx [/itex]
 
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  • #2
JasonHathaway said:

Homework Statement



Evaluate [itex] \iint\limits_S \vec{A} . \vec{n} ds[/itex] over the plane [itex] x^{2}+y^{2}=16[/itex], where [itex]\vec{A}=z\vec{i}+x\vec{j}-3y^{2}\vec{k} [/itex] and S is a part from the plane and R was projected over xz-plane.

Homework Equations



Surface Integral and Double Integration.


The Attempt at a Solution



This is an answered problem, but I didn't get how to determine the integration limits

I understand that I have to integrate with respect to x and z due the fact the region is projected over "xz-plane", and I've to get the limits from the plane equation.

The limits integration in the solution are [itex] \int_0^5 \int_0^4 dz dx [/itex]

##x^2+y^2=16## is not a plane. It's a circular cylinder standing on the xy plane. And you haven't told us how high it goes in the z direction. Draw a picture to see what its projection on the xz plane would look like.
 
  • #3
And that's what confusing me, there's no height. So the problem is wrong, isn't?
 
  • #4
I can't make sense of the problem statement. What is R? Is this quoted word for word?
 

FAQ: Determining double integral limits

How do you determine the limits for a double integral?

The limits for a double integral depend on the region of integration and the type of coordinate system being used. For rectangular coordinates, the limits are determined by the x and y values of the boundaries of the region. For polar coordinates, the limits are typically based on the angle of rotation and the radius of the region. In general, the limits should encompass the entire region of integration.

Can the limits for a double integral be negative?

Yes, the limits for a double integral can be negative. This is especially true for polar coordinates, where the angle of rotation can be negative. The limits should be chosen in a way that encompasses the entire region of integration, regardless of whether they are positive or negative.

How do you change the order of integration for a double integral?

To change the order of integration for a double integral, you can use the concept of Fubini's theorem. This theorem states that the order of integration can be changed as long as the limits for the new order are still valid for the region of integration. This can be done by converting the integral from rectangular to polar coordinates or vice versa, depending on the original coordinate system.

Can the limits for a double integral be variable?

Yes, the limits for a double integral can be variable. This is often the case when dealing with triple integrals, where the limits can depend on multiple variables. In some cases, it may be necessary to use a change of variables to express the limits in terms of a single variable.

What is the significance of the limits in a double integral?

The limits in a double integral represent the boundaries of the region being integrated. They determine the extent of the integration and are crucial in obtaining an accurate result. Choosing appropriate limits is important in order to accurately capture the area or volume being calculated.

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