Chapter 13: Problem 57
Sketch the level surface \(f(x, y, z)=k\) $$ f(x, y, z)=4 x^{2}+y^{2}+4 z^{2} ; k=16 $$
Short Answer
Expert verified
The level surface is an ellipsoid centered at the origin, elongated along the y-axis with intercepts at \( x = \pm 2 \), \( y = \pm 4 \), and \( z = \pm 2 \).
Step by step solution
01
Identify the Surface Equation
We start with the function given: \( f(x, y, z) = 4x^2 + y^2 + 4z^2 \), and we know that \( k = 16 \). To find the level surface equation, we set \( f(x, y, z) = k \), which gives us the equation \( 4x^2 + y^2 + 4z^2 = 16 \).
02
Rewrite the Equation in a Recognizable Form
To better understand the type of surface, divide each term by 16: \( \frac{4x^2}{16} + \frac{y^2}{16} + \frac{4z^2}{16} = 1 \). Simplify this to \( \frac{x^2}{4} + \frac{y^2}{16} + \frac{z^2}{4} = 1 \).
03
Identify the Surface Type
The equation \( \frac{x^2}{4} + \frac{y^2}{16} + \frac{z^2}{4} = 1 \) represents an ellipsoid centered at the origin. This is because it matches the standard form of an ellipsoid, \( \frac{x^2}{a^2} + \frac{y^2}{b^2} + \frac{z^2}{c^2} = 1 \), where \( a = 2, b = 4, c = 2 \).
04
Visualize the Ellipsoid
To sketch the ellipsoid, note that it is stretched along the y-axis more than the x and z axes. The intercepts on the axes are at \( x = \pm 2 \), \( y = \pm 4 \), and \( z = \pm 2 \). This should help in drawing an elongated ellipsoid along the y-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ellipsoid
An ellipsoid is a three-dimensional geometric surface that resembles an elongated sphere. It can be thought of as a deformed sphere, which is scaled differently along each of its three principal axes. The standard equation for an ellipsoid is given by:\[\frac{x^2}{a^2} + \frac{y^2}{b^2} + \frac{z^2}{c^2} = 1\]Here, \(a\), \(b\), and \(c\) are constants that define the semi-axis lengths along the x, y, and z directions, respectively.
This means that:
Understanding an ellipsoid can be especially helpful when exploring various physical phenomena like the shape of planets or modeling other naturally occurring objects.
This means that:
- The ellipsoid extends to \( \pm a \) units along the x-axis.
- It stretches to \( \pm b \) units along the y-axis.
- And it reaches \( \pm c \) units along the z-axis.
Understanding an ellipsoid can be especially helpful when exploring various physical phenomena like the shape of planets or modeling other naturally occurring objects.
Multivariable Calculus
Multivariable calculus is a branch of calculus that extends concepts from single-variable calculus to functions of multiple variables. This area focuses on functions that involve several variables, such as \(f(x, y, z)\). It explores concepts such as:
- Partial Derivatives: Where derivatives are taken with respect to one variable at a time, keeping others constant.
- Level Surfaces: Surfaces that represent a constant value of a multivariable function. For the function \(f(x, y, z)\), a level surface is defined by \(f(x, y, z) = k\).
- Gradient Vectors: These vectors point in the direction of the greatest rate of increase of a function, and they also help determine directions of steepest ascent or descent.
Surface Equations
Surface equations are mathematical expressions that define surfaces in three-dimensional space. These equations describe the shape, orientation, and position of the surface in respect to the coordinate axes. There are various types of surface equations, including those that define:
By manipulating the equation into a standard form through division, a clear picture of the surface as an ellipsoid emerged. Recognizing the type of surface from its equation helps in visualizing and analyzing its geometric properties and relations in multivariable contexts.
- Planes: Typically given by linear equations like \( ax + by + cz = d \).
- Quadratic Surfaces: These include ellipsoids, hyperboloids, and paraboloids, which are characteristic of second-degree polynomials.
- Implicit Surfaces: Equations like \( f(x, y, z) = 0 \) represent such surfaces without explicitly solving for one variable in terms of others.
By manipulating the equation into a standard form through division, a clear picture of the surface as an ellipsoid emerged. Recognizing the type of surface from its equation helps in visualizing and analyzing its geometric properties and relations in multivariable contexts.