Math Problem Statement

Find the general solution of the equation: u_tt - c^2 u_xx = 0 where c is constant and u = u(x, t).

Solution

The equation provided is:

uttc2uxx=0u_{tt} - c^2 u_{xx} = 0

This is the one-dimensional wave equation, where cc is the wave speed, and u=u(x,t)u = u(x, t) is the unknown function of space xx and time tt.

Solution

The general solution to the wave equation in one dimension can be found using the method of d'Alembert. The general solution is:

u(x,t)=f(xct)+g(x+ct)u(x, t) = f(x - ct) + g(x + ct)

where ff and gg are arbitrary functions determined by the initial conditions of the problem. This form represents two waves traveling in opposite directions with speed cc: one wave f(xct)f(x - ct) traveling to the right, and the other wave g(x+ct)g(x + ct) traveling to the left.

This solution arises because the wave equation can be decomposed into characteristic lines along which the solution remains constant.

Would you like a more detailed derivation of this solution or examples of initial conditions?

Here are some follow-up questions to deepen understanding:

  1. How would the solution change if we introduced a source term in the wave equation?
  2. What are some physical interpretations of the functions ff and gg in the context of waves?
  3. How does the wave speed cc affect the behavior of the solution?
  4. What are the implications of different boundary conditions, such as fixed or free ends?
  5. How would you find a specific solution given initial conditions for u(x,0)u(x, 0) and ut(x,0)u_t(x, 0)?

Tip: When solving partial differential equations like the wave equation, check if characteristic lines or coordinate transformations simplify the problem.

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Math Problem Analysis

Mathematical Concepts

Partial Differential Equations
Wave Equation
d'Alembert's Solution

Formulas

u(x, t) = f(x - ct) + g(x + ct)

Theorems

d'Alembert's Solution to the Wave Equation

Suitable Grade Level

Undergraduate