Someone Please Have Mercy and Help Me Set Up This Triple Integral

In summary, the given problem involves evaluating the triple integral of x2 within a solid that lies within a cylinder and below a cone. The solution can be simplified by using cylindrical coordinates and applying the formula for converting between Cartesian and cylindrical coordinates. The symmetry of the solid allows for an easier computation by considering the y-axis instead of the x-axis, resulting in just two regions to consider with simpler cylindrical integrals.
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Homework Statement



Evaluate ∫∫∫E x2 dV where E is the solid that lies within the cylinder x2 + y2 = 1, above the plane z = 0, and below the cone z2 = 4x2 + 4y2. Solve it using cylindrical coordinates.

Homework Equations



dxdydz = dzdrdθ, and other typical anti-derivative tricks from Calculus II.

The Attempt at a Solution



I have been attempting to solve this abomination for three straight hours and I am still nowhere. Instead of showing all of my attempts, I will show one such:

We know that the radius must remain between zero and one, since it cannot exceed the encompassing cylinder. We also know that there are no restrictions on its rotation. Lastly we know that x2 = r2 cos2 θ and that r2 = x2 + y2. Thus z = 2r. Using this, we may set up the integral as following:

0200z/2 r3 cos2 θ drdθdz
 
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  • #2
I'll make your life a lot simpler. Based on symmetry, what can you tell me about ∫∫∫E x² dV vs ∫∫∫E y² dV? Now, wouldn't computing ∫∫∫E r² dV be a lot easier? You should now have just two regions to consider, each with a simple cylindrical integral and no trig functions.
 

1. What is a triple integral?

A triple integral is a type of mathematical calculation that involves integrating a function over a three-dimensional region. It is used in various fields of science, including physics, engineering, and mathematics, to calculate volumes, masses, and other quantities.

2. When is a triple integral used?

A triple integral is used when dealing with problems that involve three variables, such as finding the volume of a three-dimensional object or calculating the probability of an event in three-dimensional space.

3. How do you set up a triple integral?

To set up a triple integral, you first need to determine the limits of integration for each variable. This is usually done by visualizing the three-dimensional region and breaking it down into smaller parts. Then, you need to determine the function to be integrated and the order of integration, which is the order in which the variables will be integrated.

4. What are the applications of triple integrals?

Triple integrals have various applications in science and engineering, including calculating volumes, masses, center of mass, moments of inertia, and electric fields in three-dimensional space. They are also used in solving differential equations and in probability and statistics.

5. Are there any tips for setting up a triple integral?

Yes, some tips for setting up a triple integral include visualizing the three-dimensional region, breaking it down into smaller parts, choosing the appropriate order of integration, and carefully determining the limits of integration for each variable. It is also helpful to practice and familiarize yourself with different types of triple integrals and their applications in order to become more proficient in setting them up.

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