85.2k views
0 votes
Evaluate the integral by changing to spherical coordinates: integral from 0 to 6, integral from 0 to 36 minus x squared, integral from 0 to 72 minus x squared minus y squared, yz dz dy dx x squared y squared.

a. 216π
b. 108π
c. 54π
d. 27π

User Jvnbt
by
7.6k points

1 Answer

5 votes

Final answer:

When converting the given integral to spherical coordinates, the integrand simplifies to zero due to symmetry properties of sine and cosine over a full period, thus the integral evaluates to 0, which is not an option listed in the question.

Step-by-step explanation:

To evaluate the integral using spherical coordinates, we first need to express the limits of integration for the variables x, y, z into spherical coordinates (ρ, θ, φ). In spherical coordinates, ρ is the radius from the origin, θ is the angle with the positive x-axis (in the xy plane), and φ is the angle from the positive z-axis.

The original integral bounds suggest that we are integrating within a cylinder whose radius squared is 36 (since the y-integral goes from 0 to 36 - x^2) and a half-sphere or dome above it (since the z-integral goes from 0 to 72 - x^2 - y^2).This solid lies above the xy-plane and is symmetric with respect to the z-axis.

Using spherical coordinates, the integrand x^2y^2 becomes ρ^4sin^3φcosθsinθ and the bounds for ρ, θ, and φ are 0 to 6, 0 to 2π, and 0 to π/2, respectively, to cover the cylinder and the half-sphere. During the conversion, we also include the Jacobian determinant, which is ρ^2sinφ for spherical coordinates.

The volume element changes from dxdydz to ρ^2sinφ dρdθdφ. The full integral in spherical coordinates is then:

0

π/2

0

0

6

ρ^6sin^4φcosθsinθ dρdθdφ.

On separating the integral and integrating with respect to ρ, θ, and φ, we find that the θ integrand is zero due to the symmetry property of sine and cosine over a full period which reduces the integral to zero. Therefore, the answer is 0.

User PeterClemmensen
by
8.1k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.