The document provides an introduction to differential equations, covering definitions, classifications, and initial-value problems. It distinguishes between ordinary and partial differential equations, as well as explicit and implicit solutions. Additionally, it discusses the role of differential equations as mathematical models in various applications.
The document provides an introduction to differential equations, covering definitions, classifications, and initial-value problems. It distinguishes between ordinary and partial differential equations, as well as explicit and implicit solutions. Additionally, it discusses the role of differential equations as mathematical models in various applications.
The document provides an introduction to differential equations, covering definitions, classifications, and initial-value problems. It distinguishes between ordinary and partial differential equations, as well as explicit and implicit solutions. Additionally, it discusses the role of differential equations as mathematical models in various applications.
The document provides an introduction to differential equations, covering definitions, classifications, and initial-value problems. It distinguishes between ordinary and partial differential equations, as well as explicit and implicit solutions. Additionally, it discusses the role of differential equations as mathematical models in various applications.
Definitions and Terminology Introduction The words differential and equation certainly suggest solving some kind of equation that contains derivatives.
But before you start solving anything, you must learn
some of the basic definitions and terminology of the subject Definition The derivative dy/dx of a function y = ϕ (x) is itself another function ϕ '(x) found by an appropriate rule. For example, the function is differentiable on the interval (- ∞, ∞), and its derivative is If we replace in the last equation by the symbol y, we obtain Classification by Type If a differential equation contains only ordinary derivatives of one or more functions with respect to a single independent variable it is said to be an ordinary differential equation (ODE). Classification by Type An equation involving only partial derivatives of one or more functions of two or more independent variables is called a partial differential equation (PDE). Notation Throughout this text, ordinary derivatives will be written using either the Leibniz notation dy/dx, d2y/dx2, d3y/dx3, • • • , or the prime notation y', y", y"', .... Classification by Order The order of a differential equation (ODE or PDE) is the order of the highest derivative in the equation. The differential equations
are examples of a second-order ordinary differential equation
and a fourth-order partial differential equation, respectively. Classification by Linearity The equations
are, in turn, examples of linear first-, second-, and third-order
ordinary differential equations. The equations
are examples of nonlinear first-, second-, and fourth-order ordinary
differential equations, respectively Solution Explicit and Implicit Solutions You should be familiar with the terms explicit and implicit functions from your study of calculus. A solution in which the dependent variable is expressed solely in terms of the independent variable and constants is said to be an explicit solution. Systems of Differential Equations Up to this point we have been discussing single differential equations containing one unknown function.
But often in theory, as well as in many applications, we must
deal with systems of differential equations Initial-Value Problems Initial-Value Problem We are often interested in problems in which we seek a solution y(x) of a differential equation so that y(x) satisfies prescribed side conditions-that is, conditions that are imposed on the unknown y(x) or on its derivatives Differential Equations as Mathematical Models Mathematical Models Steps in the modeling process Mathematical Models
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(Applications of Mathematics,) Mariano Giaquinta, Stefan Hildebrandt - Calculus of Variations II. The Hamilton Formalism - The Hamiltonian Formalism - v. 2 (2006, Springer)