Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Implicit Functions: Lagrange Multipliers

Description

This lecture covers the concept of implicit functions and Lagrange multipliers. It starts by introducing the implicit function theorem for a function f: R^2 -> R, where f is continuously differentiable. The theorem states that if f(a, b) = 0 for some point (a, b), then there exists a function y(x) defined in a neighborhood of a such that (x, y(x)) satisfies f(x, y(x)) = 0. The demonstration shows the existence of suitable intervals for x and y, ensuring the monotonicity of the function. Finally, it concludes by proving that the function ga is strictly monotone at the point (a, b) and ga(b) = 0.

Official source

Related concepts (15)

Implicit function

In mathematics, an implicit equation is a relation of the form where R is a function of several variables (often a polynomial). For example, the implicit equation of the unit circle is An implicit function is a function that is defined by an implicit equation, that relates one of the variables, considered as the value of the function, with the others considered as the arguments. For example, the equation of the unit circle defines y as an implicit function of x if −1 ≤ x ≤ 1, and y is restricted to nonnegative values.

Implicit function theorem

In multivariable calculus, the implicit function theorem is a tool that allows relations to be converted to functions of several real variables. It does so by representing the relation as the graph of a function. There may not be a single function whose graph can represent the entire relation, but there may be such a function on a restriction of the domain of the relation. The implicit function theorem gives a sufficient condition to ensure that there is such a function. More precisely, given a system of m equations fi (x1, .

Differentiable function

In mathematics, a differentiable function of one real variable is a function whose derivative exists at each point in its domain. In other words, the graph of a differentiable function has a non-vertical tangent line at each interior point in its domain. A differentiable function is smooth (the function is locally well approximated as a linear function at each interior point) and does not contain any break, angle, or cusp. If x0 is an interior point in the domain of a function f, then f is said to be differentiable at x0 if the derivative exists.

Semi-differentiability

In calculus, a branch of mathematics, the notions of one-sided differentiability and semi-differentiability of a real-valued function f of a real variable are weaker than differentiability. Specifically, the function f is said to be right differentiable at a point a if, roughly speaking, a derivative can be defined as the function's argument x moves to a from the right, and left differentiable at a if the derivative can be defined as x moves to a from the left.

Smoothness

In mathematical analysis, the smoothness of a function is a property measured by the number of continuous derivatives it has over some domain, called differentiability class. At the very minimum, a function could be considered smooth if it is differentiable everywhere (hence continuous). At the other end, it might also possess derivatives of all orders in its domain, in which case it is said to be infinitely differentiable and referred to as a C-infinity function (or function).

Related lectures (35)

Derivability of Reciprocal Function MOOC: Analysis I MOOC: Analysis I (part 5): Continuous and derivable functions, the derivative function

Covers the derivative of the reciprocal function and its properties.

Vector spaces and norms

Covers vector spaces, differentiable functions, scalar product, and norms in depth.

Linear Approximation and Derivative Parametric

Covers linear approximation, parametric derivatives, and differentiability conditions on intervals.

Implicit Differentiation

Explores implicit differentiation and the Implicit Function Theorem for finding unique local functions.

Differentiable Functions: Definitions and Interpretation