Math Problem Statement

solve

The parametric curve x(t) = -2sin(2t), y(t) = 2(cos(2t) + 1), z(t) = -4cos(t) lies on the following surfaces: 1. The sphere of equation 2. The cone of equation 3. The circular cylinder of equation 4. The parabolic cylinder of equation

Solution

To solve this problem, we need to analyze the given parametric equations:

x(t)=2sin(2t),y(t)=2(cos(2t)+1),z(t)=4cos(t)x(t) = -2 \sin(2t), \quad y(t) = 2(\cos(2t) + 1), \quad z(t) = -4 \cos(t)

We are asked to find the equations of surfaces that this parametric curve lies on, specifically for:

  1. A sphere
  2. A cone
  3. A circular cylinder
  4. A parabolic cylinder

Let's analyze each component to determine the corresponding surface equations.

1. Sphere of Equation

To check if this curve lies on a sphere, we would typically check if x2+y2+z2=r2x^2 + y^2 + z^2 = r^2 for some constant rr. Let's try to substitute and simplify.

Using the parametric expressions: x2=(2sin(2t))2=4sin2(2t)x^2 = (-2 \sin(2t))^2 = 4 \sin^2(2t) y2=(2(cos(2t)+1))2=4(cos(2t)+1)2y^2 = \left(2(\cos(2t) + 1)\right)^2 = 4(\cos(2t) + 1)^2 z2=(4cos(t))2=16cos2(t)z^2 = (-4 \cos(t))^2 = 16 \cos^2(t)

We need to sum these: x2+y2+z2=4sin2(2t)+4(cos(2t)+1)2+16cos2(t)x^2 + y^2 + z^2 = 4 \sin^2(2t) + 4(\cos(2t) + 1)^2 + 16 \cos^2(t)

By simplifying this expression (using trigonometric identities as necessary), we should aim to find a constant radius if possible.

2. Cone of Equation

For a cone, the general form is z2=x2+y2z^2 = x^2 + y^2. Substitute z=4cos(t)z = -4 \cos(t), x=2sin(2t)x = -2 \sin(2t), and y=2(cos(2t)+1)y = 2(\cos(2t) + 1), and see if this identity holds.

3. Circular Cylinder of Equation

For a circular cylinder, we would have an equation in the form x2+y2=R2x^2 + y^2 = R^2. Let's examine whether we can simplify x(t)x(t) and y(t)y(t) to fit this form for some constant RR.

4. Parabolic Cylinder of Equation

A parabolic cylinder generally has the form y=ax2+by = ax^2 + b. Substitute y=2(cos(2t)+1)y = 2(\cos(2t) + 1) and see if it can be expressed in terms of x=2sin(2t)x = -2 \sin(2t) in a way that resembles a parabolic form.

I'll proceed with detailed calculations to verify each of these surfaces.Here are the results of the calculations:

  1. Sphere: The sum x2+y2+z2x^2 + y^2 + z^2 simplifies to 32cos2(t)32 \cos^2(t). This is not a constant, so the curve does not lie on a true sphere.

  2. Cone: The expression z2(x2+y2)z^2 - (x^2 + y^2) simplifies to 00, which indicates that z2=x2+y2z^2 = x^2 + y^2. Therefore, the curve does lie on a cone with the equation: z2=x2+y2z^2 = x^2 + y^2

  3. Circular Cylinder: The expression x2+y2x^2 + y^2 simplifies to 16cos2(t)16 \cos^2(t), which is not a constant, so the curve does not lie on a circular cylinder.

Now, let's check for the parabolic cylinder by analyzing if yy can be expressed as a function of x2x^2.The expression for y2(x2)2y - 2\left(\frac{x}{2}\right)^2 simplifies to 2sin2(2t)+2cos(2t)+2-2 \sin^2(2t) + 2 \cos(2t) + 2, which is not a constant or a direct parabolic form. Therefore, the curve does not lie on a parabolic cylinder.

Summary of Results

  1. Sphere: No suitable equation, as x2+y2+z2x^2 + y^2 + z^2 is not constant.
  2. Cone: The curve lies on the cone with the equation: z2=x2+y2z^2 = x^2 + y^2
  3. Circular Cylinder: No suitable equation, as x2+y2x^2 + y^2 is not constant.
  4. Parabolic Cylinder: No suitable equation for a parabolic cylinder.

Would you like further details on these calculations, or do you have any questions?

Related Questions

  1. How does trigonometric simplification help in verifying surface equations?
  2. Can a curve lie on multiple types of surfaces simultaneously?
  3. What other types of surfaces can parametric curves lie on?
  4. How do we generalize surface equations for higher-dimensional spaces?
  5. What methods can be used to visualize the intersection of a curve with a surface?

Tip

When verifying if a curve lies on a surface, checking if certain expressions reduce to constants is crucial.

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Math Problem Analysis

Mathematical Concepts

Parametric equations
Surface equations
Trigonometric identities
Coordinate geometry

Formulas

x^2 + y^2 + z^2 = r^2 (Sphere equation)
z^2 = x^2 + y^2 (Cone equation)
x^2 + y^2 = R^2 (Circular cylinder equation)
y = ax^2 + b (Parabolic cylinder equation)

Theorems

-

Suitable Grade Level

Undergraduate level