Math Problem Statement

Solution

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The problem statement appears to be:

"Evaluate the triple integral Ef(x,y,z)dV\iiint_E f(x, y, z) \, dV, where f(x,y,z)=x2+y2+z2f(x, y, z) = x^2 + y^2 + z^2, over the part of the ball x2+y2+z29x^2 + y^2 + z^2 \leq 9 defined by z2z \geq 2."

To solve this triple integral:

  1. Transform to Spherical Coordinates: x=ρsinϕcosθ,y=ρsinϕsinθ,z=ρcosϕx = \rho \sin\phi \cos\theta, \quad y = \rho \sin\phi \sin\theta, \quad z = \rho \cos\phi with the Jacobian determinant ρ2sinϕ\rho^2 \sin\phi.

  2. Limits of Integration:

    • ρ\rho ranges from 0 to 3 (since the radius of the ball is 3).
    • ϕ\phi ranges from 0 to cos1(23)\cos^{-1}\left(\frac{2}{3}\right) (the angle corresponding to z2z \geq 2).
    • θ\theta ranges from 0 to 2π2\pi.
  3. Integral Setup: Ef(x,y,z)dV=02π0cos1(2/3)03(ρ2sin2ϕcos2θ+ρ2sin2ϕsin2θ+ρ2cos2ϕ)ρ2sinϕdρdϕdθ\iiint_E f(x, y, z) \, dV = \int_{0}^{2\pi} \int_{0}^{\cos^{-1}(2/3)} \int_{0}^{3} \left( \rho^2 \sin^2\phi \cos^2\theta + \rho^2 \sin^2\phi \sin^2\theta + \rho^2 \cos^2\phi \right) \rho^2 \sin\phi \, d\rho \, d\phi \, d\theta Simplifying the integrand: 02π0cos1(2/3)03ρ4(sin2ϕ(cos2θ+sin2θ)+cos2ϕ)sinϕdρdϕdθ\int_{0}^{2\pi} \int_{0}^{\cos^{-1}(2/3)} \int_{0}^{3} \rho^4 \left( \sin^2\phi (\cos^2\theta + \sin^2\theta) + \cos^2\phi \right) \sin\phi \, d\rho \, d\phi \, d\theta Since cos2θ+sin2θ=1\cos^2\theta + \sin^2\theta = 1: 02π0cos1(2/3)03ρ4(sin2ϕ+cos2ϕ)sinϕdρdϕdθ\int_{0}^{2\pi} \int_{0}^{\cos^{-1}(2/3)} \int_{0}^{3} \rho^4 \left( \sin^2\phi + \cos^2\phi \right) \sin\phi \, d\rho \, d\phi \, d\theta =02π0cos1(2/3)03ρ4sinϕdρdϕdθ= \int_{0}^{2\pi} \int_{0}^{\cos^{-1}(2/3)} \int_{0}^{3} \rho^4 \sin\phi \, d\rho \, d\phi \, d\theta

  4. Separating Integrals:

    • The integral with respect to ρ\rho: 03ρ4dρ=ρ5503=355=2435\int_{0}^{3} \rho^4 \, d\rho = \left. \frac{\rho^5}{5} \right|_0^3 = \frac{3^5}{5} = \frac{243}{5}
    • The integral with respect to ϕ\phi: 0cos1(2/3)sinϕdϕ=cosϕ0cos1(2/3)=cos(cos1(23))+cos(0)=23+1=13\int_{0}^{\cos^{-1}(2/3)} \sin\phi \, d\phi = \left. -\cos\phi \right|_0^{\cos^{-1}(2/3)} = -\cos\left(\cos^{-1}\left(\frac{2}{3}\right)\right) + \cos(0) = -\frac{2}{3} + 1 = \frac{1}{3}
    • The integral with respect to θ\theta: 02πdθ=2π\int_{0}^{2\pi} d\theta = 2\pi
  5. Final Calculation: Ef(x,y,z)dV=(2435)(13)(2π)=243×2π15=486π15=162π5\iiint_E f(x, y, z) \, dV = \left( \frac{243}{5} \right) \left( \frac{1}{3} \right) \left( 2\pi \right) = \frac{243 \times 2\pi}{15} = \frac{486\pi}{15} = \frac{162\pi}{5}

Therefore, the value of the triple integral is 162π5\boxed{\frac{162\pi}{5}}.

Would you like any more details or have any questions?

Here are 8 related questions for further practice:

  1. Evaluate E1dV\iiint_E 1 \, dV over the same region.
  2. Evaluate the integral ExdV\iiint_E x \, dV over the same region.
  3. What is the volume of the part of the ball x2+y2+z29x^2 + y^2 + z^2 \leq 9 defined by z2z \geq 2?
  4. Compute Eex2+y2+z2dV\iiint_E e^{x^2 + y^2 + z^2} \, dV over the same region.
  5. Evaluate EzdV\iiint_E z \, dV over the same region.
  6. Evaluate the integral Esin(x2+y2+z2)dV\iiint_E \sin(x^2 + y^2 + z^2) \, dV over the same region.
  7. How would the integral change if the region is defined by x2+y2+z216x^2 + y^2 + z^2 \leq 16 and z2z \geq 2?
  8. Find the centroid of the region defined by x2+y2+z29x^2 + y^2 + z^2 \leq 9 and z2z \geq 2.

Tip: Always double-check the limits of integration, especially when switching coordinate systems.

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Math Problem Analysis

Mathematical Concepts

Triple integrals
Spherical coordinates
Volume calculations

Formulas

Triple integral setup in spherical coordinates
Volume of a sphere

Theorems

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Suitable Grade Level

College