Chapter 11: Problem 30
Find the equation of the surface that results when the curve \(4 x^{2}-3 y^{2}=12\) in the \(x y\) -plane is revolved about the \(x\) -axis.
Short Answer
Expert verified
The equation of the surface is \(4x^2 - 3z^2 = 12\).
Step by step solution
01
Identify the Curve
The given curve is a hyperbola, described by the equation \(4x^2 - 3y^2 = 12\). This is a horizontal hyperbola centered at the origin in the \(xy\)-plane.
02
Solve for y in terms of x
To revolve the curve around the \(x\)-axis, first solve for \(y\). Rearrange the equation \(4x^2 - 3y^2 = 12\) to isolate \(y^2\): \[-3y^2 = 12 - 4x^2\] or \[y^2 = \frac{4x^2 - 12}{-3} = \frac{4x^2 - 12}{3}\].
03
Consider Revolution Around the x-axis
When a curve is revolved around the \(x\)-axis, the resulting surface is defined by \(x\) and the radius \(y\). Here, \(z\) represents values below and above the \(x\)-axis and \(z^2\) will replace \(y^2\): \(z^2 = \frac{4x^2 - 12}{3}\).
04
Formulate the Surface Equation
Replace \(y^2\) with \(z^2\) to get the equation of the surface of revolution: \[4x^2 - 3z^2 = 12\]. This is the standard form of the hyperbolic cylinder obtained upon revolving the hyperbola around the \(x\)-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Surface of Revolution
A surface of revolution is a three-dimensional surface obtained by rotating a curve around a straight line, known as the axis of revolution. The process is like spinning an object around a string or a rod, where the curve generates a surface as if it left a trail while spinning.
- The axis of revolution can be the x-axis, y-axis, or any other line in the coordinate plane.
- A well-known example is when a curve is revolved around an axis. The curve's every point sweeps out a circle with the axis as the center when it's rotated around that axis.
- This helps to visualize and understand solid figures in terms of simpler two-dimensional shapes.
Revolving Curves
Revolving curves is the mathematical procedure where a two-dimensional shape or curve is turned around a line (usually an axis) to create a three-dimensional object.
- This is a foundational concept in advanced geometry and calculus, enabling the calculation of volumes and surface areas of complex shapes by simplifying them to known forms.
- The result of revolving curves is often shapes like cylinders, cones, or spheres, depending on the original curve's nature.
- For a hyperbola, as in our exercise, revolving it about the x-axis produces a hyperbolic cylinder.
Hyperbola
A hyperbola is a type of conic section or two-dimensional curve from the intersection of a plane with both halves of a double cone. It comprises two disconnected curves called branches that resemble mirrored bows or the stylized wings of a butterfly.
- Each branch of a hyperbola can be thought of as creating arch-like paths, opening in opposite directions from a central point known as the center.
- The general equation of a hyperbola is \(Ax^2 - By^2 = C\) or \(Ay^2 - Bx^2 = C\), distinguishing it from other conics like ellipses and parabolas.
- In the provided exercise, the curve \4x^2 - 3y^2 = 12\ represents a hyperbola in the x-y plane, centered at the origin.