Calculus 3 Multi-Integration (volume)

In summary, the author is trying to find out where to start with integrating the surface z=4(x²+y²). He is having trouble understanding the symmetry and how to do the integration. He ends up using a sketch and a graph to help him. He states that he is not the type of person who just wants the answer, he wants to understand the reasoning behind it.
  • #1
IAmGroot48
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Homework Statement
In this particular question the following is stated.

Find the volume of the region below z=4(x²+y²), above z=0, and between the two cylinders x²+y²=1² and x²+y²=3².
Relevant Equations
This question doesn't necessarily say if the two cylinders are intersecting each other, so I'm not 100% clear how to go on about this question. If I could get an Idea on how to set this up or solve it. I'd be able to figure out the rest.
Pending
 
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  • #2
:welcome:

I'm not sure where the ambiguity is. The cylinders are concentric and the volume in question lies between them.
 
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  • #3
I feel like I may be over thinking this--I have ADHD so sometimes I have to read things over and over again to imagine what I am trying to do. Am I suppose to use triple integration for this or is this something double integration can do. What throws me off is the cylinder within the cylinder and then the region below z=4(x²+y²). I can't grasp where I am suppose to begin.
 
  • #4
IAmGroot48 said:
I feel like I may be over thinking this--I have ADHD so sometimes I have to read things over and over again to imagine what I am trying to do. Am I suppose to use triple integration for this or is this something double integration can do. What throws me off is the cylinder within the cylinder and then the region below z=4(x²+y²). I can't grasp where I am suppose to begin.
Initially I would think you could just do a single integration along z because of the symmetry of the surfaces. Can you try making a couple sketches to help you understand the geometry? Do one sketch from the side (say, looking down the x-axis with the y-axis to the right and z upward), and do one sketch in a perspective view looking at an angle down from the side (like along the line x=y=z)...

EDIT -- Mark mentions a double integral below, so I could be wrong about the simplification to a single integration...
 
  • #5
IAmGroot48 said:
I feel like I may be over thinking this--I have ADHD so sometimes I have to read things over and over again to imagine what I am trying to do. Am I suppose to use triple integration for this or is this something double integration can do. What throws me off is the cylinder within the cylinder and then the region below z=4(x²+y²). I can't grasp where I am suppose to begin.
Can you sketch a graph of the surface ##z = 4(x^2 + y^2)##? It's a paraboloid with its vertex at the origin, its axis along the z-axis, and opening upward. The two cylinders also have their axes along the z-axis.

The volume of the enclosed region can be calculated with a double integral.
 
  • #6
InkedGraphing_Calculator_3D_jM8InWyBjy_LI.jpg
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This is what I am getting as far as the sketch. The paraboloid does indeed touch the origin, and then the surface z=0 is shown as a plane at well z=0. so from z=0 to z=4(x²+y²) is the first integration? In other words does the set up look like 4(x²+y²) dydx? and the first integration is from x²+y²=1² (bottom) to x²+y²=3² (top)?

Just Fyi: I am not the type of person who just wants the answer. I want to be able to find the answer myself for the most part but I want to understand why or how.
 
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  • #7
Mark44 said:
Can you sketch a graph of the surface ##z = 4(x^2 + y^2)##? It's a paraboloid with its vertex at the origin, its axis along the z-axis, and opening upward. The two cylinders also have their axes along the z-axis.

The volume of the enclosed region can be calculated with a double integral.
Was this rhetorical?
 
  • #8
IAmGroot48 said:
Was this rhetorical?
Parabolic!
 
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  • #9
I apologize I'm not sure what you're meaning when you only say parabolic.
 
  • #10
IAmGroot48 said:
I apologize I'm not sure what you're meaning when you only say parabolic.
Only that it's a parabolic question, rather than a rhetorical one.
 
  • #11
I feel there was a funny thrown in there, but its almost got me thinking...slightly sparked an ember...
 
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  • #12
I suggest you look at cylindrical coordinates and figure our the range for ##r## or ##\rho##, whichever you use, for each value of ##z##.
 
  • #13
IAmGroot48 said:
This is what I am getting as far as the sketch.
Wow, nice sketch! What software package did you use to do that?
 
  • #14
IAmGroot48 said:
View attachment 293873|

This is what I am getting as far as the sketch. The paraboloid does indeed touch the origin, and then the surface z=0 is shown as a plane at well z=0. so from z=0 to z=4(x²+y²) is the first integration? In other words does the set up look like 4(x²+y²) dydx? and the first integration is from x²+y²=1² (bottom) to x²+y²=3² (top)?

Just Fyi: I am not the type of person who just wants the answer. I want to be able to find the answer myself for the most part but I want to understand why or how.

berkeman said:
Wow, nice sketch! What software package did you use to do that?
Normally I use autocad. But this is a simple piece of software you can easily get for free. You can get it on Microsoft Store and it's called Graphing Calculator 3, there's a free version and a pro version.
 
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  • #15
PeroK said:
I suggest you look at cylindrical coordinates and figure our the range for ##r## or ##\rho##, whichever you use, for each value of ##z##.
Ill show you the work I've done so far. I think it finally clicked. "I think"
 
  • #16
Also...I am a firm believer every single website should have a Dark Mode from this point on 2022 and above. The bright white colors just murder my eyes...😵

-A Computer Engineer Major
 
  • #17
We used to have different skins that you could choose from. Let me do a little searching...
 
  • #18
IAmGroot48 said:
Was this rhetorical?
No, not at all. I didn't know you had access to a graphing tool.
 
  • #19
IAmGroot48 said:
.I am a firm believer every single website should have a Dark Mode from this point on 2022 and above.
I spoke with the Admin, and he will look at adding a Dark Mode in the 2022 updates. :smile:
 
  • #20
Oh you rock! Thats awesome! I truly believe all websits should have that option. We're moving into a technological generation where a huge majority of our hardware is being ran by software so i feel we need to have dark mode to lessen the health concerns to our eyes. Sounds insane but a huge help to our optical system. Thank you.
 
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  • #21
As for this question. This is what I came up with.
 

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  • #22
IAmGroot48 said:
I am a firm believer every single website should have a Dark Mode from this point on 2022 and above. The bright white colors just murder my eyes.
My computers have an option to turn down the brightness. Have you tried that?Personally, I really dislike dark mode, as I find it harder to read, but hey, different strokes for different folks.
 
  • #23
Yeah I am on the computer almost all day, so I need to take breaks from time to time. So even when I am learning to code I put my whole visual studio on a dark type format. I also use a software called Rainmeter to control all of my computers setting. Its an overlay for your whole desktop setting.
 
  • #24

Related to Calculus 3 Multi-Integration (volume)

1. What is multi-integration in Calculus 3?

Multi-integration in Calculus 3 refers to the process of calculating the volume of a solid or region in three-dimensional space using multiple integrals. It involves breaking down the three-dimensional shape into smaller, simpler shapes and integrating the function over each of these shapes to find the total volume.

2. What is the difference between single and multi-integration in Calculus 3?

The main difference between single and multi-integration in Calculus 3 is the number of variables involved. Single integration involves integrating a function with respect to one variable, while multi-integration involves integrating a function with respect to multiple variables. In Calculus 3, multi-integration is used to find the volume of three-dimensional shapes, while single integration is used for finding the area under a curve in two-dimensional space.

3. How is the volume of a solid or region calculated using multi-integration?

The volume of a solid or region can be calculated using multi-integration by breaking the three-dimensional shape into smaller, simpler shapes such as cylinders, spheres, or cones. The volume of each of these shapes can be calculated using single integration, and then the total volume can be found by summing up the volumes of all the smaller shapes.

4. What are some real-world applications of multi-integration in Calculus 3?

Multi-integration in Calculus 3 has many real-world applications, such as in engineering, physics, and economics. It can be used to calculate the volume of complex three-dimensional objects, such as the volume of a water tank, the amount of material needed to construct a building, or the volume of a chemical solution in a container. It can also be used to find the center of mass of a three-dimensional object or to calculate the work done by a force on a three-dimensional object.

5. What are some tips for solving multi-integration problems in Calculus 3?

Some tips for solving multi-integration problems in Calculus 3 include breaking down the three-dimensional shape into smaller, simpler shapes, choosing the correct order of integration, and carefully setting up the limits of integration. It is also important to have a good understanding of single integration and the properties of integrals. Practicing with various examples and seeking help from a tutor or professor can also be helpful in mastering multi-integration problems.

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