Calculus
Textbooks
Boundless Calculus
Advanced Topics in Single-Variable Calculus and an Introduction to Multivariable Calculus
Partial Derivatives
Calculus Textbooks Boundless Calculus Advanced Topics in Single-Variable Calculus and an Introduction to Multivariable Calculus Partial Derivatives
Calculus Textbooks Boundless Calculus Advanced Topics in Single-Variable Calculus and an Introduction to Multivariable Calculus
Calculus Textbooks Boundless Calculus
Calculus Textbooks
Calculus
Concept Version 7
Created by Boundless

Functions of Several Variables

Multivariable calculus is the extension of calculus in one variable to calculus in more than one variable.

Learning Objective

  • Identify areas of application of multivariable calculus


Key Points

    • Multivariable calculus can be applied to analyze deterministic systems that have multiple degrees of freedom.
    • Unlike a single variable function $f(x)$, for which the limits and continuity of the function need to be checked as $x$ varies on a line ($x$-axis), multivariable functions have infinite number of paths approaching a single point.
    • In multivariable calculus, gradient, Stokes', divergence, and Green theorems are specific incarnations of a more general theorem: the generalized Stokes' theorem.

Terms

  • deterministic

    having exactly predictable time evolution

  • divergence

    a vector operator that measures the magnitude of a vector field's source or sink at a given point, in terms of a signed scalar


Full Text

Multivariable calculus (also known as multivariate calculus) is the extension of calculus in one variable to calculus in more than one variable : the differentiated and integrated functions involve multiple variables, rather than just one. Multivariable calculus can be applied to analyze deterministic systems that have multiple degrees of freedom. Functions with independent variables corresponding to each of the degrees of freedom are often used to model these systems, and multivariable calculus provides tools for characterizing the system dynamics.

A Scalar Field

A scalar field shown as a function of $(x,y)$. Extensions of concepts used for single variable functions may require caution.

Multivariable calculus is used in many fields of natural and social science and engineering to model and study high-dimensional systems that exhibit deterministic behavior. Non-deterministic, or stochastic, systems can be studied using a different kind of mathematics, such as stochastic calculus. Quantitative analysts in finance also often use multivariate calculus to predict future trends in the stock market.

As we will see, multivariable functions may yield counter-intuitive results when applied to limits and continuity. Unlike a single variable function $f(x)$, for which the limits and continuity of the function need to be checked as $x$ varies on a line ($x$-axis), multivariable functions have infinite number of paths approaching a single point.Likewise, the path taken to evaluate a derivative or integral should always be specified when multivariable functions are involved.

We have also studied theorems linking derivatives and integrals of single variable functions. The theorems we learned are gradient theorem, Stokes' theorem, divergence theorem, and Green's theorem. In a more advanced study of multivariable calculus, it is seen that these four theorems are specific incarnations of a more general theorem, the generalized Stokes' theorem, which applies to the integration of differential forms over manifolds.

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