Chapter 4: Problem 20
For the following exercises, find the level curves of each function at the indicated value of \(c\) to visualize the given function. $$f(x, y)=x^{2}-y ; c=1,2$$
Short Answer
Expert verified
The level curves are \( y = x^2 - 1 \) for \( c=1 \) and \( y = x^2 - 2 \) for \( c=2 \).
Step by step solution
01
Understand Level Curves
Level curves of a function \( f(x, y) \) are sets of points \( (x, y) \) such that \( f(x, y) = c \) for some constant \( c \). These curves display where the function takes on certain values and are useful for visualizing the behavior of the function in the plane.
02
Set the Function Equal to \( c \)
For \( f(x, y) = x^2 - y \), we need to find the level curves for \( c=1 \) and \( c=2 \). This means setting \( x^2 - y = c \).
03
Solve for \( y \) in Terms of \( x \) for \( c=1 \)
Set the function equal to 1: \( x^2 - y = 1 \). Solve for \( y \):\[ y = x^2 - 1 \]This represents the level curve for \( c=1 \).
04
Solve for \( y \) in Terms of \( x \) for \( c=2 \)
Set the function equal to 2: \( x^2 - y = 2 \). Solve for \( y \):\[ y = x^2 - 2 \]This represents the level curve for \( c=2 \).
05
Describe the Level Curves
The level curve for \( c=1 \) is the curve \( y = x^2 - 1 \), a parabola opening upwards with its vertex at \( (0, -1) \). The level curve for \( c=2 \) is \( y = x^2 - 2 \), which is also a parabola opening upwards with its vertex at \( (0, -2) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Contour Plots
Contour plots are a way to represent three-dimensional surfaces on a two-dimensional plane. Imagine a topographic map: instead of showing hills and valleys in 3D, it uses lines to represent points of equal elevation. Similarly, in mathematics, contour plots use level curves to describe how a function behaves over a range of values.
These plots are especially useful when dealing with multivariable functions. For the function given in the exercise, the level curves are found where the equation takes a constant value, such as 1 or 2. The contour plot would illustrate these curves, showing how the function's output changes over the plane.
Key points for contour plots:
These plots are especially useful when dealing with multivariable functions. For the function given in the exercise, the level curves are found where the equation takes a constant value, such as 1 or 2. The contour plot would illustrate these curves, showing how the function's output changes over the plane.
Key points for contour plots:
- Each contour line indicates where the function has the same output.
- The spacing between lines can indicate the steepness of the function. Closer lines mean steeper changes.
- They are essential for visualizing complex functions without needing a 3D graph.
Multivariable Functions
Multivariable functions are functions with more than one input. They often look like this: \( f(x, y) \), where the function depends on variables \( x \) and \( y \). These functions are prevalent in many fields, including engineering, physics, and economics because they model scenarios where multiple factors influence an outcome.
In the exercise, the function \( f(x, y) = x^2 - y \) is a simple multivariable function. It illustrates how changes in both \( x \) and \( y \) affect the function's overall output. By using level curves, we can see constant output values across different inputs.
Here are some basics of multivariable functions:
In the exercise, the function \( f(x, y) = x^2 - y \) is a simple multivariable function. It illustrates how changes in both \( x \) and \( y \) affect the function's overall output. By using level curves, we can see constant output values across different inputs.
Here are some basics of multivariable functions:
- They often require more advanced math techniques, like calculus, for analyzing.
- They are represented graphically by surfaces rather than lines or curves.
- Level curves are a handy way to simplify their analysis.
Parabolas
Parabolas are a type of curve that you'll often encounter in mathematics, particularly in quadratic equations. They have a characteristic "U" shape and can open either upwards or downward depending on the equation.
In this specific exercise, both level curves \( y = x^2 - 1 \) and \( y = x^2 - 2 \) are parabolas. Here's what's interesting:
In this specific exercise, both level curves \( y = x^2 - 1 \) and \( y = x^2 - 2 \) are parabolas. Here's what's interesting:
- Both parabolas open upwards since the terms \( x^2 \) are positive.
- These curves are similar, just shifted vertically on the graph. For \( c=1 \), the vertex is at \( (0, -1) \), and for \( c=2 \), it's at \( (0, -2) \).
- Parabolas are symmetrical along their vertex, meaning if you fold the graph at the vertex, both sides would match perfectly.