Functions of Several Variables Quiz
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the domain of the function f(x, y) = 4 - x² - y²?

  • The closed disk defined by x² + y² ≤ 4 (correct)
  • All points in R²
  • The open disk defined by x² + y² < 4
  • The closed disk defined by x² + y² = 4

For the function g(x, y, z) = x² + y² + z², where is the function undefined?

  • At points outside the plane formed by x + y + z = 1
  • At all points in R³
  • At the points where x, y, and z are zero
  • At the origin (0, 0, 0) (correct)

What does the equation M = aL^b represent in the study of allometry?

  • The relationship between length and area
  • The relationship between volume and surface area
  • The relationship between mass and length (correct)
  • The relationship between mass and volume

How do you determine the boundaries of the domain for f(x, y) = 4 - x² - y²?

<p>By solving the equation 4 - x² - y² = 0 (A)</p> Signup and view all the answers

What is the form of the resistance function in a parallel arrangement of resistances x and y?

<p>xy/(x + y) (D)</p> Signup and view all the answers

When calculating the limit of f(x, y) at (0, 0), what is the initial substitution?

<p>Replacing x with 0 and y with 0 (A)</p> Signup and view all the answers

What type of geometric shape represents the domain of definition for the function f(x, y) = 4 - x² - y²?

<p>A circle (A)</p> Signup and view all the answers

In which situation would the limit of a function as (x, y) approaches (0, 0) yield infinity?

<p>When there is a division by a variable that approaches zero (D)</p> Signup and view all the answers

What is the purpose of using the change of variable in polar coordinates when addressing indeterminate forms?

<p>To simplify the limit by transforming coordinates into a circular form. (B)</p> Signup and view all the answers

In the limit process, what indicates that the limit does not exist?

<p>The limit depends on the chosen variable or direction. (D)</p> Signup and view all the answers

What is the result when evaluating the limit of the function $(x, y) \to (0, 0)$ for $\lim \frac{x^2 + 2y}{x + y + 3}$?

<p>32 (D)</p> Signup and view all the answers

For the function $\lim \frac{xy}{x^2 + y^2}$ as $(x, y) \to (0, 0)$, what can be concluded from its dependence on $ heta$?

<p>The limit does not exist due to its behavior with respect to $ heta$. (D)</p> Signup and view all the answers

What does the limit $\lim \sqrt{xy}$ as $(x, y) \to (0, 0)$ illustrate?

<p>It converges to zero regardless of direction. (A)</p> Signup and view all the answers

When evaluating the limit using the transformation $Y = tX$, what is the role of the variable t in the limit process?

<p>It controls the direction in which the limit is approached. (B)</p> Signup and view all the answers

What does the limit process at points $(x_0, y_0)$ evaluate as $(X, Y) \to (0, 0)$?

<p>It assesses the function at specified coordinates. (D)</p> Signup and view all the answers

What is the implication of evaluating $\lim \frac{\ln(X + 1 + Y)}{Y}$ as $(x,y) \to (1, +\infty)$?

<p>The limit approaches zero as Y tends to infinity. (B)</p> Signup and view all the answers

What is the continuity condition for a function f at the point (x0, y0)?

<p>lim f(x, y) = f(x0, y0) as (x, y) approaches (x0, y0) (B)</p> Signup and view all the answers

What is the result of setting Y = tX in the limit L = lim (sin((1+t)X)/X) as X approaches 0?

<p>1 + t (C)</p> Signup and view all the answers

For the function f(x, y) = x^2y / (x^2 + y^2) when (x, y) ≠ (0, 0), what does the limit approach as (x, y) approaches (0, 0)?

<p>0 (C)</p> Signup and view all the answers

What defines the partial derivative ∂f/∂x of a multi-variable function f?

<p>Derivative of f while treating all variables except x as constants (A)</p> Signup and view all the answers

What is the first partial derivative ∂f/∂y of the function f(x, y, z) = xe^(2z) + ln(xyz)?

<p>y (C)</p> Signup and view all the answers

What are the second order partial derivatives of a function f(x, y)?

<p>Partial derivatives of ∂f/∂x and ∂f/∂y (C)</p> Signup and view all the answers

For the function f(x, y) = x^2 + xy^2 + 3y^3 + e^(xy), what is the value of ∂f/∂y?

<p>2xy + 9y^2 + e^(xy) (A)</p> Signup and view all the answers

What is the correct form of the partial derivative ∂f/∂x when f(x1, x2, ..., xn) is defined for n variables?

<p>Derive considering only xk as variable and others as constants (C)</p> Signup and view all the answers

What is the notation for the second order partial derivative with respect to x?

<p>∂^2f/∂x^2 (C)</p> Signup and view all the answers

Which of the following statements describes a local maximum?

<p>f(x, y) ≤ f(x0, y0) for all (x, y) near (x0, y0) (C)</p> Signup and view all the answers

If W is calculated at a critical point and W > 0, what can be concluded if R < 0?

<p>The point is a local maximum. (A)</p> Signup and view all the answers

When W < 0 at a critical point (x0, y0), what is the situation concerning extrema?

<p>The function has a saddle point. (B)</p> Signup and view all the answers

What condition must be met for the second order mixed partial derivatives to be equal?

<p>The second order derivatives must be continuous. (B)</p> Signup and view all the answers

For the given function g(x, y) = x^2 + xy^2 + 3y^3 + e^{xy}, what is the second order partial derivative with respect to y?

<p>2x + 18y + x^2 e^{xy} (D)</p> Signup and view all the answers

What is the expression for W in terms of R, S, and T?

<p>RT - S^2 (D)</p> Signup and view all the answers

What are the conditions that define a critical point for a two-variable function?

<p>Both partial derivatives equal zero. (A)</p> Signup and view all the answers

What are the coordinates of the critical points identified in the problem?

<p>(1, 1), (1, -1), (-1, 1), (-1, -1) (C)</p> Signup and view all the answers

At which critical point does the function have a maximum?

<p>M4 = (-1, -1) (B)</p> Signup and view all the answers

What value of W indicates that the function does not have an extremum at M2 and M3?

<p>-36 (A)</p> Signup and view all the answers

What is the formula for the differential of a function with two variables?

<p>df = ∂f/∂x dx + ∂f/∂y dy (B)</p> Signup and view all the answers

How is the maximum error on z indicated when calculating errors in a function?

<p>∆z = | ∂f/∂x | ∆x + | ∂f/∂y | ∆y (A)</p> Signup and view all the answers

What is the value of the error on the area S when x = 10 ± 0.1 and y = 20 ± 0.2?

<p>200 ± 4 m² (A)</p> Signup and view all the answers

What condition must be met for a function to have a minimum at a critical point?

<p>W &gt; 0 and R &gt; 0 (D)</p> Signup and view all the answers

What do the letters R, S, and T represent in the context of the second derivative test?

<p>Determinants of the Hessian matrix (D)</p> Signup and view all the answers

Flashcards

Function of Several Variables

A function that takes multiple input variables (e.g., x, y, z) and produces a single output value.

Domain of a Function

The set of all possible input values (x1, x2, ..., xn) for which the function is defined.

Limit of a Function

Determines the value of the function as the input values (x, y) approach a specific point (x0, y0).

Continuity of a Function

A function is continuous at a point (x0, y0) if its limit at that point exists and equals the function's value at that point.

Signup and view all the flashcards

Allometry

The study of relationships between the size of different parts of an organism and the size of the entire organism.

Signup and view all the flashcards

Parallel Resistance Function

The resistance of two resistors connected in parallel, given by the formula xy/(x+y) where x and y are the individual resistances.

Signup and view all the flashcards

Two-Variable Function

A function that takes two input variables (e.g., x, y) and produces a single output value.

Signup and view all the flashcards

Determining the Domain of a Two-Variable Function

The process of determining the set of all possible input values (x, y) for which a function is defined, often involving identifying boundaries and testing points.

Signup and view all the flashcards

Limit of a Two-Variable Function

A technique to evaluate the limit of a function of two variables as it approaches a point where the function is indeterminate.

Signup and view all the flashcards

Indeterminate Form

A form of a limit where the numerator and denominator both approach zero, infinity, or a combination of both.

Signup and view all the flashcards

Polar Coordinates Limit Evaluation

The limit of a function as a point (x, y) approaches a point (0, 0) where the function is indeterminate, using polar coordinates (r, θ) to parameterize (x, y).

Signup and view all the flashcards

Parametric Limit Evaluation

The limit of a function as a point (x, y) approaches a point (0, 0) where the function is indeterminate, using a parameter t to control the direction of approach along a line.

Signup and view all the flashcards

Existence of Limit

A two-variable limit exists if and only if the limit is finite and does not depend on the chosen direction of approach.

Signup and view all the flashcards

Limit at a Point

Finding the limit of a function as a point (x, y) approaches a point (x0, y0 ), using a transformation that shifts the origin to (x0, y0).

Signup and view all the flashcards

Limit at Infinity

Finding the limit of a function as a point (x, y) approaches a point (x0, ∞), using a transformation that shifts the origin to (x0, 0) and introduces Y = 1/y.

Signup and view all the flashcards

Double Limit at Infinity

Finding the limit of a function as a point (x, y) approaches infinity, using a transformation that scales the origin by 1/x and 1/y.

Signup and view all the flashcards

Limit of a function at infinity

The limit of a function f(x, y) as (x, y) approaches (∞, ∞) is equal to the limit of f(X, Y) as (X, Y) approaches (0, 0) by setting Y=tX.

Signup and view all the flashcards

Partial derivative

The derivative of the function f(x1, x2, ..., xn) with respect to a specific variable xk, treating all other variables as constants.

Signup and view all the flashcards

Second Order Partial Derivatives

The derivative of ∂f/∂x and ∂f/∂y, where f(x, y) is a two-variable function.

Signup and view all the flashcards

Partial Derivative of f(x,y,z) with respect to x

The derivative of f(x, y, z) with respect to x, considering y and z as constants.

Signup and view all the flashcards

Partial Derivative of f(x,y,z) with respect to y

The derivative of f(x, y, z) with respect to y, considering x and z as constants.

Signup and view all the flashcards

Partial Derivative of f(x,y,z) with respect to z

The derivative of f(x, y, z) with respect to z, considering x and y as constants.

Signup and view all the flashcards

Partial Differentiation

The process of finding the derivative of a function involving multiple variables, where each variable is treated as a single entity and differentiated separately.

Signup and view all the flashcards

Critical Point

A point where all the first-order partial derivatives of a function are zero or undefined. Think of it as a potential turning point.

Signup and view all the flashcards

Local Extrema (Maxima or Minima)

A point where a function has a maximum or minimum value compared to its surrounding points.

Signup and view all the flashcards

Mixed Partial Derivative

The second-order partial derivative where we differentiate with respect to one variable and then the other (e.g., ∂²f/∂y∂x).

Signup and view all the flashcards

Clairaut's Theorem

A condition where the mixed partial derivatives are equal at a point, assuming they are continuous. This tells us the order of differentiation doesn't matter.

Signup and view all the flashcards

Saddle Point

A point that's a critical point but not an extremum. Think of a saddle point on a horse - going up in one direction and down in another!

Signup and view all the flashcards

Second Derivative Test for Multivariable Functions

A tool to determine the type of extremum at a critical point. It's a formula involving second-order partial derivatives.

Signup and view all the flashcards

Differential

A small change in the function's output due to small changes in the input variables. It approximates the function's behavior near a point.

Signup and view all the flashcards

Discriminant (W)

An expression that determines the type of critical point. It's calculated as RT − S 2, where R, S, and T are second-order partial derivatives of the function.

Signup and view all the flashcards

Extremum

The maximum or minimum value of a function within a certain region. It can occur at a critical point or on the boundary of the region.

Signup and view all the flashcards

Error Propagation

An approximation of the error in the function's output based on the errors in the input variables. It uses the differential to estimate uncertainty.

Signup and view all the flashcards

Study Notes

Functions of Several Variables

  • Definition and Examples: Rn represents an n-tuple of real numbers (x1, x2, ..., xn). A function of n real variables is an application f from a subset D of Rn to values in R. This is written as f: D → R(x1, x2, ..., xn) → f(x1, x2, ..., xn). (Alternative notation exists)

Two-variable Functions

  • Domain of Definition: The domain of a function of two variables f(x, y), denoted as Df, is the set of all (x, y) pairs in the plane where the function produces real values.

  • Determining the Domain: To find the domain: (1) Write the initial condition, (2) Determine boundaries, and (3) Graphically represent and identify regions contributing to Df using points within those regions.

Limits and Continuity

  • Limit at (0,0): To find the limit of a function as (x, y) approaches (0,0), replace x and y with 0 initially. If an indeterminate form results, convert to polar coordinates (x = r cos θ, y = r sin θ).

  • Limit Existence: A limit exists if the result doesn't depend on the direction (θ) and is finite. Otherwise, it does not exist.

  • Limit at (xâ‚€, yâ‚€): For a limit at a point (xâ‚€, yâ‚€), substitute X= x – xâ‚€ and Y= y- yâ‚€. The limit becomes lim(X,Y)→(0,0) f(X+xâ‚€, Y+yâ‚€).

  • Continuity: A function f is continuous at (xâ‚€, yâ‚€) if lim(x,y)→(xâ‚€,yâ‚€) f(x, y) = f(xâ‚€, yâ‚€).

Partial Derivatives

  • Definition: The partial derivative of an n-variable function f(x1, x2, ..., xn) with respect to xk is the derivative of the function xk → f(x1, x2, ..., xk, ..., xn) considering other variables as constants.

  • Notation: Partial derivatives of f with respect to x are written as ∂f/∂x

  • Higher-order Derivatives: Second-order partial derivatives and higher derivatives exist and can be calculated in a similar manner.

Critical Points and Extrema

  • Critical Points: A critical point (x, y) for a two-variable function f satisfies ∂f/∂x = 0 and ∂f/∂y = 0.

  • Extrema: Local maximum or minimum points are critical points. Use second-order partial derivatives to determine whether a critical point is a local maximum, minimum, or saddle point. Define R=∂2f/∂x2, S=∂2f/∂x∂y, and T=∂2f/∂y2. Then evaluate W = RT - S2 and the sign of R and W determines the type to confirm a maximum, minimum, or neither.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Description

Test your understanding of functions of several variables, focusing on definitions, examples, and the important concepts of domains, limits, and continuity in two-variable functions. This quiz will help reinforce your knowledge and skills in multivariable calculus.

More Like This

Max and Min of Multivariable Function
3 questions
Calculus Multivariable Functions
5 questions
Funciones de Varias Variables
97 questions

Funciones de Varias Variables

WellEstablishedLeaningTowerOfPisa178 avatar
WellEstablishedLeaningTowerOfPisa178
Limits and Continuity of Functions of Several Variables
10 questions
Use Quizgecko on...
Browser
Browser