问题


There is a single choice question about college mathematics. Answer the question by replying A, B, C or D.
Question: Let C be the circle in the yz-plane whose equation is (y - 3)^2 + z^2 = 1. If C is revolved around the z-axis, the surface generated is a torus. What is the equation of this torus?
A. x^2 + y^2 + z^2 + 8 = 6y
B. (x^2 + y^2 + z^2)^2 = 8 + 36(x^2 + z^2)
C. (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + z^2)
D. (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2)
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

A torus is a doughnut-shaped surface of revolution generated by revolving a circle in three-dimensional space about an axis coplanar with the circle. If the circle is centered at (0, 3, 0) and has radius 1, and is revolved around the z-axis, the equation of the torus can be written in the form:

(x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2)

This equation represents a torus centered at the origin with major radius 3 and minor radius 1.

The correct answer is D.
D
deepseekr1

The circle \( C \) in the yz-plane has the equation \((y - 3)^2 + z^2 = 1\), centered at \((0, 3, 0)\) with radius 1. When revolved around the z-axis, the generated torus has a major radius \( R = 3 \) (distance from the z-axis to the circle's center) and a minor radius \( r = 1 \). The standard torus equation when rotated around the z-axis is:

\[
\left(\sqrt{x^2 + y^2} - 3\right)^2 + z^2 = 1.
\]

Expanding and rearranging:

1. Expand the left-hand side:
\[
x^2 + y^2 - 6\sqrt{x^2 + y^2} + 9 + z^2 = 1.
\]
2. Simplify:
\[
x^2 + y^2 + z^2 + 8 = 6\sqrt{x^2 + y^2}.
\]
3. Square both sides to eliminate the square root:
\[
(x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2).
\]

This matches **Option D**. The other options incorrectly place terms (e.g., \( x^2 + z^2 \) in Option C) or introduce linear terms (Option A), which do not align with the derived equation.

**Answer:** D
D
gpto1 After revolving the circle \( C \) around the \( z \)-axis, we get a torus whose points satisfy a specific equation.

Starting with the circle's equation \( (y - 3)^2 + z^2 = 1 \), we parameterize the circle as:
\( y = 3 + \cos \theta \)
\( z = \sin \theta \)

When this circle is revolved around the \( z \)-axis, the \( x \) and \( y \) coordinates transform using \( \phi \), the angle of rotation:
\( x = (3 + \cos \theta) \sin \phi \)
\( y = (3 + \cos \theta) \cos \phi \)

Calculating \( x^2 + y^2 \):
\( x^2 + y^2 = (3 + \cos \theta)^2 \)

Let \( s = \sqrt{x^2 + y^2} \), so:
\( s = 3 + \cos \theta \)

Since \( \sin^2 \theta + \cos^2 \theta = 1 \), and \( \cos \theta = s - 3 \), it follows that:
\( z^2 + (s - 3)^2 = 1 \)

Simplify and rearrange:
\( x^2 + y^2 + z^2 - 6s + 8 = 0 \)

Bring \( 6s \) to the other side and square both sides:
\( (x^2 + y^2 + z^2 + 8)^2 = [6 \sqrt{x^2 + y^2}]^2 \)
\( (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2) \)

This matches option D.

**Answer: D**
D
GPT-4o To find the equation of the torus generated by revolving the circle \( (y - 3)^2 + z^2 = 1 \) around the z-axis, we need to consider the geometry of the problem.

The given circle is centered at \( (0, 3, 0) \) in the yz-plane with a radius of 1. When this circle is revolved around the z-axis, it generates a torus with:

- The major radius \( R \) (distance from the center of the tube to the center of the torus) being 3 (the distance from the y-axis to the center of the circle).
- The minor radius \( r \) (radius of the tube) being 1 (the radius of the circle).

The standard form of the equation of a torus with these parameters is:

\[ \left( \sqrt{x^2 + y^2} - R \right)^2 + z^2 = r^2 \]

Substituting \( R = 3 \) and \( r = 1 \), we get:

\[ \left( \sqrt{x^2 + y^2} - 3 \right)^2 + z^2 = 1 \]

To eliminate the square root, we can square both sides:

\[ \left( \sqrt{x^2 + y^2} - 3 \right)^2 + z^2 = 1 \]

\[ (\sqrt{x^2 + y^2})^2 - 2 \cdot 3 \cdot \sqrt{x^2 + y^2} + 3^2 + z^2 = 1 \]

\[ x^2 + y^2 - 6\sqrt{x^2 + y^2} + 9 + z^2 = 1 \]

Now, isolating \( \sqrt{x^2 + y^2} \):

\[ x^2 + y^2 + z^2 + 8 = 6 \sqrt{x^2 + y^2} \]

Square both sides again:

\[ \left( x^2 + y^2 + z^2 + 8 \right)^2 = (6 \sqrt{x^2 + y^2})^2 \]

\[ \left( x^2 + y^2 + z^2 + 8 \right)^2 = 36 (x^2 + y^2) \]

Thus, the equation of the torus is:

\[ \left( x^2 + y^2 + z^2 + 8 \right)^2 = 36 (x^2 + y^2) \]

Therefore, the correct answer is:

C. \((x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2)\)
D
llama3.1-70B-Instruct

B
D
llama3.1-405B-Instruct

The equation of the torus can be found by considering the distance of any point on the torus from the center of the torus (which is at the origin) and the distance of that point from the z-axis.

Let's denote the distance of any point (x, y, z) on the torus from the z-axis as r, where r^2 = x^2 + y^2. The distance of the point (x, y, z) from the center of the torus (origin) is given by the distance formula as sqrt(x^2 + y^2 + z^2).

The equation of the torus can be derived by considering the relationship between these distances. The distance of any point on the torus from the center of the torus (origin) is the hypotenuse of a right-angled triangle, where one leg is the distance of the point from the z-axis (r) and the other leg is the distance of the point from the yz-plane (which is z).

Using the Pythagorean theorem, we can write:

sqrt(x^2 + y^2 + z^2)^2 = (sqrt(x^2 + y^2))^2 + z^2

Simplifying, we get:

x^2 + y^2 + z^2 = r^2 + z^2

Now, we need to incorporate the equation of the circle C, which is (y - 3)^2 + z^2 = 1. We can rewrite this equation as:

y^2 - 6y + 9 + z^2 = 1

Simplifying, we get:

y^2 + z^2 = 6y - 8

Substituting this equation into the equation for the torus, we get:

x^2 + y^2 + z^2 = 6y - 8 + x^2

Simplifying, we get:

x^2 + y^2 + z^2 + 8 = 6y

Therefore, the equation of the torus is x^2 + y^2 + z^2 + 8 = 6y.

The correct answer is A.
D
DeepSeek-Coder-V2 C D
Qwen2-72B-Instruct C. (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + z^2) D
baichuan4 The correct answer is C. (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + z^2) D
doubao C

The equation of a torus generated by revolving a circle (y - b)^2 + z^2 = a^2 around the z-axis is (x^2 + y^2 + z^2 - b^2 - a^2)^2 = 4a^2(x^2 + z^2). In this case, a = 1 and b = 3, so the equation is (x^2 + y^2 + z^2 - 9 - 1)^2 = 4(x^2 + z^2), which simplifies to (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + z^2).
D
minimax The equation of the circle C in the yz-plane is given by \((y - 3)^2 + z^2 = 1\). When this circle is revolved around the z-axis, the resulting surface is a torus.

The torus can be described by the equation \((x^2 + y^2 + z^2 + R)^2 = 4R^2(x^2 + z^2)\), where \(R\) is the distance from the center of the tube to the center of the torus (the major radius), and the radius of the tube itself is \(r\). In this case, the circle has a radius of 1, and its center is at the point (0, 3, 0), which means that the major radius \(R\) is 3.

Plugging in \(R = 3\) into the general torus equation, we get:
\((x^2 + y^2 + z^2 + 3)^2 = 4(3)^2(x^2 + z^2)\)
\((x^2 + y^2 + z^2 + 3)^2 = 36(x^2 + z^2)\)

This matches option B, so the correct answer is:

B. \((x^2 + y^2 + z^2)^2 = 8 + 36(x^2 + z^2)\)
D
kimi The equation of a circle in the yz-plane is given by (y - 3)^2 + z^2 = 1. When this circle is revolved around the z-axis, it forms a torus. The equation of a torus can be derived by considering the radius of the circle in the yz-plane as the minor radius (r) of the torus and the distance from the z-axis to the center of the circle as the major radius (R) of the torus.

The equation of a torus in cylindrical coordinates (r, θ, z) is given by:

\[ (r - R)^2 + z^2 = r^2 \]

where r is the minor radius, R is the major radius, and θ is the angle around the z-axis.

In Cartesian coordinates, this equation becomes:

\[ (x^2 + y^2 - R^2)^2 + z^2 = r^2 \]

Given that the minor radius r is 1 (from the equation of the circle) and the major radius R is 3 (the center of the circle is at y = 3), we can substitute these values into the equation:

\[ (x^2 + y^2 - 3^2)^2 + z^2 = 1^2 \]
\[ (x^2 + y^2 - 9)^2 + z^2 = 1 \]

Now, let's look at the options given:

A. \( x^2 + y^2 + z^2 + 8 = 6y \) - This does not match the torus equation.
B. \( (x^2 + y^2 + z^2)^2 = 8 + 36(x^2 + z^2) \) - This does not match the torus equation.
C. \( (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + z^2) \) - This does not match the torus equation.
D. \( (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2) \) - This does not match the torus equation.

None of the options match the correct equation of the torus. However, if we correct the equation for the torus to match the given circle's equation, it should be:

\[ (x^2 + (y - 3)^2 + z^2 - 1)^2 + z^2 = 1 \]

This equation is not listed among the options, but it is the correct equation for the torus formed by revolving the given circle around the z-axis. If we were to simplify this equation, we would get:

\[ (x^2 + y^2 - 6y + 9 + z^2 - 1)^2 + z^2 = 1 \]
\[ (x^2 + y^2 - 6y + 8 + z^2)^2 + z^2 = 1 \]

This equation is still not among the options, but it is the correct form of the equation for the torus. It seems there might be a mistake in the provided options.
D
wenxinyiyan C D
zhipu To determine the equation of the torus generated by revolving the circle \( C \) in the \( yz \)-plane around the \( z \)-axis, let's analyze the given circle and the resulting torus.

The equation of the circle \( C \) is:
\[ (y - 3)^2 + z^2 = 1 \]

This circle has its center at \( (3, 0) \) in the \( yz \)-plane and a radius of 1.

When this circle is revolved around the \( z \)-axis, each point on the circle traces out a toroidal surface. To derive the equation of the torus, we need to convert the coordinates of the circle into 3D coordinates and then express the resulting surface equation.

In the \( yz \)-plane, the circle is parameterized by:
\[ y = 3 + \cos(\theta) \]
\[ z = \sin(\theta) \]
where \( \theta \) is the parameter.

When revolved around the \( z \)-axis, the point \( (y, z) \) in the \( yz \)-plane generates a circle in the \( xy \)-plane with radius \( y \). Thus, the coordinates in 3D space become:
\[ x = y \cos(\phi) \]
\[ y = y \sin(\phi) \]
\[ z = z \]
where \( \phi \) is the angle of rotation around the \( z \)-axis.

Substituting \( y = 3 + \cos(\theta) \) and \( z = \sin(\theta) \) into these equations, we get:
\[ x = (3 + \cos(\theta)) \cos(\phi) \]
\[ y = (3 + \cos(\theta)) \sin(\phi) \]
\[ z = \sin(\theta) \]

To find the equation of the torus, we need to eliminate the parameters \( \theta \) and \( \phi \). The key is to recognize that the distance from the origin to the center of the torus (which lies on the \( y \)-axis at \( y = 3 \)) is 3, and the radius of the circle being revolved is 1.

The standard form of the equation of a torus centered at \( (R, 0, 0) \) with a tube radius \( r \) is:
\[ ( \sqrt{x^2 + y^2} - R )^2 + z^2 = r^2 \]

For our torus:
\[ R = 3 \]
\[ r = 1 \]

Thus, the equation becomes:
\[ ( \sqrt{x^2 + y^2} - 3 )^2 + z^2 = 1 \]

Expanding and simplifying this equation:
\[ ( \sqrt{x^2 + y^2} - 3 )^2 + z^2 = 1 \]
\[ x^2 + y^2 - 6\sqrt{x^2 + y^2} + 9 + z^2 = 1 \]
\[ x^2 + y^2 + z^2 - 6\sqrt{x^2 + y^2} + 9 = 1 \]
\[ x^2 + y^2 + z^2 - 6\sqrt{x^2 + y^2} + 8 = 0 \]

To match this with the given choices, we square both sides to eliminate the square root:
\[ ( x^2 + y^2 + z^2 + 8 )^2 = 36(x^2 + y^2) \]

Thus, the correct equation of the torus is:
\[ ( x^2 + y^2 + z^2 + 8 )^2 = 36(x^2 + y^2) \]

Therefore, the correct answer is:
\[ \boxed{D} \]
D
gpto1 After revolving the circle \( C \) around the \( z \)-axis, we get a torus whose points satisfy a specific equation.

Starting with the circle's equation \( (y - 3)^2 + z^2 = 1 \), we parameterize the circle as:
\( y = 3 + \cos \theta \)
\( z = \sin \theta \)

When this circle is revolved around the \( z \)-axis, the \( x \) and \( y \) coordinates transform using \( \phi \), the angle of rotation:
\( x = (3 + \cos \theta) \sin \phi \)
\( y = (3 + \cos \theta) \cos \phi \)

Calculating \( x^2 + y^2 \):
\( x^2 + y^2 = (3 + \cos \theta)^2 \)

Let \( s = \sqrt{x^2 + y^2} \), so:
\( s = 3 + \cos \theta \)

Since \( \sin^2 \theta + \cos^2 \theta = 1 \), and \( \cos \theta = s - 3 \), it follows that:
\( z^2 + (s - 3)^2 = 1 \)

Simplify and rearrange:
\( x^2 + y^2 + z^2 - 6s + 8 = 0 \)

Bring \( 6s \) to the other side and square both sides:
\( (x^2 + y^2 + z^2 + 8)^2 = [6 \sqrt{x^2 + y^2}]^2 \)
\( (x^2 + y^2 + z^2 + 8)^2 = 36(x^2 + y^2) \)

This matches option D.

**Answer: D**
D
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