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

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SUMMARY

The discussion focuses on evaluating the triple integral ∫∫∫E x² dV, where E is defined by the cylinder x² + y² = 1, the plane z = 0, and the cone z² = 4x² + 4y². The solution employs cylindrical coordinates, with the integral set up as ∫₀² ∫₀²π ∫₀^(z/2) r³ cos² θ dr dθ dz. The discussion emphasizes the symmetry between x² and y² integrals, suggesting that computing ∫∫∫E r² dV simplifies the process significantly.

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  • Understanding of triple integrals in calculus
  • Familiarity with cylindrical coordinates
  • Knowledge of anti-derivative techniques from Calculus II
  • Concept of symmetry in integrals
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  • Learn about the properties of symmetry in multivariable calculus
  • Practice solving triple integrals involving different solid regions
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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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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.
 

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