Volume Rot. Region: Find Vol. Bounded by Curve, Y=x^2 & x=y^2, Rotated about Y=1

In summary, the region bounded by the curves y=x^2 and x=y^2, when rotated about the line y=1, has a volume of 11pi/30. However, there was an error in the solution attempt, specifically in the coefficient 2/3 in the third term of the antiderivative. Once corrected, the correct answer can be obtained.
  • #1
tree.lee
10
0

Homework Statement



How do you find the volume of the solid obtained by rotating the region bounded by the given curves about the specified lines?

I keep getting a negative number and I"m becoming so frustrated! 11pi/30 is the answer in the textbook. Thank you so very much in advance!

Homework Equations



y=x^2
x=y^2
about y=1

The Attempt at a Solution



Area:
pi[(1-x^2)^2 - (1-x^(1/2))^2)]

Integral:
pi[1-2x^2+x^4-1+2x^(1/2)-x) between x=0 and x= 1

Antiderivative:
pi[(1/5x)^5-(2/3)x^3 + (2/3)x^(3/2)-(1/2)x^2]

Soln:
pi((2/10)-(5/10)) = -3pi/10??
 
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  • #3
tree.lee said:

Homework Statement



How do you find the volume of the solid obtained by rotating the region bounded by the given curves about the specified lines?

I keep getting a negative number and I"m becoming so frustrated! 11pi/30 is the answer in the textbook. Thank you so very much in advance!

Homework Equations



y=x^2
x=y^2
about y=1

The Attempt at a Solution



Area:
pi[(1-x^2)^2 - (1-x^(1/2))^2)]

Integral:
pi[1-2x^2+x^4-1+2x^(1/2)-x) between x=0 and x= 1

Antiderivative:

pi[(1/5x)^5-(2/3)x^3 + (2/3)x^(3/2)-(1/2)x^2]
You have a mistake in the line above. The coefficient 2/3 in the third term is wrong. I get what you reported to be the correct answer.
tree.lee said:
Soln:
pi((2/10)-(5/10)) = -3pi/10??
 

Related to Volume Rot. Region: Find Vol. Bounded by Curve, Y=x^2 & x=y^2, Rotated about Y=1

1. What is the formula for finding the volume of a region bounded by the curves y = x^2 and x = y^2, rotated about the line y = 1?

The formula for finding the volume of a region bounded by two curves and rotated about a line is given by V = π∫(R(x)^2 - r(x)^2)dx, where R(x) is the outer radius and r(x) is the inner radius.

2. How do you determine the outer and inner radius for this region?

The outer radius is the distance from the rotation axis (y = 1) to the outer curve (x = y^2), which is given by R(x) = y^2 - 1. The inner radius is the distance from the rotation axis to the inner curve (y = x^2), which is given by r(x) = x^2 - 1.

3. Can you provide an example of how to set up the integral for this volume?

Let's say we want to find the volume of the region bounded by y = x^2 and x = y^2, rotated about y = 1. First, we need to set up the integral: V = π∫(R(x)^2 - r(x)^2)dx. Then, we plug in the values for R(x) and r(x): V = π∫((y^2 - 1)^2 - (x^2 - 1)^2)dx. Finally, we integrate with respect to x from the x-values where the curves intersect, which can be found by setting y = x^2 and x = y^2 equal to each other and solving for x.

4. Is there a way to check if my answer is correct?

Yes, you can use a graphing calculator or software to graph the region and the rotated volume. Then, you can use the "volume" function to find the volume and compare it to your calculated answer.

5. Can this concept be applied to other regions and curves?

Yes, this concept of finding the volume of a region bounded by curves and rotated about a line can be applied to other regions and curves as long as the region is "solid" (no holes) and the curves intersect at two points.

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