Chapter 11: Problem 14
Sketch the surfaces in Exercises \(13-44\) $$z=y^{2}-1$$
Short Answer
Expert verified
The surface is a parabolic cylinder with axis parallel to the \(x\)-axis, shifting the parabola \(z = y^2 - 1\) along \(x\).
Step by step solution
01
Understand the Equation
The given equation is \(z = y^2 - 1\). This is a function in three-dimensional space where \(z\) is expressed in terms of \(y\). The equation suggests for every \(y\), \(z\) is translated vertically by -1. This is a quadratic function in terms of \(y\).
02
Identify the Shape
Since the equation is \(z = y^2 - 1\), it's a parabolic surface where for each constant \(x\), the curve is a parabola opening in the positive \(z\) direction. The minimum point of the parabola is at \(z = -1\) when \(y = 0\). This is a parabola facing upwards shifted down by 1 unit along the \(z\)-axis.
03
Describe the Sketch
Visualize the surface: Imagine a two-dimensional parabola, \(z = y^2 - 1\), with its vertex at \( (0,0,-1) \), and now extend this two-dimensional shape infinitely along the \(x\)-axis. This forms a parabolic cylinder with its axis parallel to the \(x\)-axis.
04
Draw the Sketch
To sketch the graph:- Draw the \(y\)-\(z\) plane, focusing on \(z = y^2 - 1\), a parabola with its vertex at \((0,-1)\).- Extend this parabola infinitely along the \(x\)-axis, creating a three-dimensional parabolic cylinder.- Ensure to show the symmetry about the \(z\)-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Three-Dimensional Space
In math, we often deal with two-dimensional graphs, like lines or circles. However, in three-dimensional space, or 3D space, things get a bit more complex but also way more interesting.
Three-dimensional space lets us graph functions like our equation, \(z = y^2 - 1\), by introducing an extra axis. Think of 3D space as a real-world scenario, like height, length, and width.
Three-dimensional space lets us graph functions like our equation, \(z = y^2 - 1\), by introducing an extra axis. Think of 3D space as a real-world scenario, like height, length, and width.
- In this case, we have three axes: \(x\), \(y\), and \(z\).
- The \(x\)-axis generally runs left to right.
- The \(y\)-axis runs back and forth.
- The \(z\)-axis goes up and down.
Quadratic Functions
Quadratic functions are a vital part of mathematics, often forming parabolas. A typical quadratic function has the form \(y = ax^2 + bx + c\).
In our exercise, the quadratic part is \(z = y^2 - 1\), which can be understood as:
The interesting twist in our problem is that this curvature doesn't relate to \(x\) at all, making it constant; hence, for each \(x\)-value, \(z\) is determined solely by \(y\).
This simplifies its plotting in three-dimensional space, focusing on translating the 2D quadratic idea into a 3D graph.
In our exercise, the quadratic part is \(z = y^2 - 1\), which can be understood as:
- \(y^2\) causing the curve to open upwards since it's positive.
- The \(-1\) shifts the entire curve downward by one unit.
The interesting twist in our problem is that this curvature doesn't relate to \(x\) at all, making it constant; hence, for each \(x\)-value, \(z\) is determined solely by \(y\).
This simplifies its plotting in three-dimensional space, focusing on translating the 2D quadratic idea into a 3D graph.
Parabolic Cylinder
The concept of a parabolic cylinder is fascinating because it combines parabolas and cylinders in 3D space.
Visualize a parabolic cylinder by starting with a simple 2D parabola, like \(z = y^2 - 1\), on the \(y\)-\(z\) plane. Now, imagine stretching this parabola along the \(x\)-axis:
This shape happens to model certain physical phenomena and can appear in architecture or physics, illustrating how math can bridge into real-life applications.
Visualize a parabolic cylinder by starting with a simple 2D parabola, like \(z = y^2 - 1\), on the \(y\)-\(z\) plane. Now, imagine stretching this parabola along the \(x\)-axis:
- This creates a shape that never bends or curves in the \(x\)-direction.
- For any fixed \(x\), you'll find the same parabola.
- Its main axis is parallel to the \(x\)-axis, which is constant and why it's called a *cylinder*.
This shape happens to model certain physical phenomena and can appear in architecture or physics, illustrating how math can bridge into real-life applications.