Evaluate: ∫02∫23∫0𝑟cos𝜃+𝑟sin𝜃+5(𝑟cos𝜃)𝑟𝑑𝑧𝑑𝑟𝑑𝜃Group of answer choices65𝜋/335𝜋/465𝜋/475𝜋/4 PreviousNext No
Question
Evaluate: ∫02∫23∫0𝑟cos𝜃+𝑟sin𝜃+5(𝑟cos𝜃)𝑟𝑑𝑧𝑑𝑟𝑑𝜃Group of answer choices65𝜋/335𝜋/465𝜋/475𝜋/4 PreviousNext No
Solution
The given integral is in cylindrical coordinates. The limits of the integral suggest that we are integrating over a cylindrical volume. The limits for z are from 0 to r, for r are from 2 to 3, and for θ are from 0 to 2π.
The integrand is rcos(θ) + rsin(θ) + 5(rcos(θ)) which simplifies to 6rcos(θ) + rsin(θ).
We can integrate this step by step:
-
First, integrate with respect to z. The integral of a constant with respect to z is just the constant times z. So, we get ∫02∫23[6rcos(θ)z + rsin(θ)z] evaluated from z=0 to z=r drdθ.
-
Substituting the limits for z, we get ∫02∫23[6r^2cos(θ) + r^2sin(θ)] drdθ.
-
Now, integrate with respect to r. The integral of r^2 with respect to r is (1/3)r^3. So, we get ∫02[(1/3)*6r^3cos(θ) + (1/3)r^3sin(θ)] evaluated from r=2 to r=3 dθ.
-
Substituting the limits for r, we get ∫02[(54cos(θ) - 16cos(θ)) + (27sin(θ) - 8sin(θ))] dθ = ∫02[38cos(θ) + 19sin(θ)] dθ.
-
Finally, integrate with respect to θ. The integral of cos(θ) with respect to θ is sin(θ), and the integral of sin(θ) with respect to θ is -cos(θ). So, we get [38sin(θ) - 19cos(θ)] evaluated from θ=0 to θ=2π.
-
Substituting the limits for θ, we get 38sin(2π) - 19cos(2π) - 38sin(0) + 19cos(0) = 0 - 191 - 0 + 191 = 0.
So, the value of the given triple integral is 0.
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.