[Math] Difference between constants, arbitrary constants and variables in differential equation

calculusordinary differential equations

The general solution of the differential equation $y''+\omega^2y=0$ can be written as: $$y=\alpha\cos{(\omega(t-c))}+\beta\sin{(\omega(t-c))}$$
Is it correct to say that:

  1. $\omega$ and $c$ are constants
  2. $\alpha$ and $\beta$ are arbitrary constants
  3. $t$ is a variable

QUESTION: What is the difference between constants, arbitrary constants and variables?

Best Answer

It is totally correct.

The solution of the equation, the function, depends on the value of t (called, the variable).

Also, the constants are properties of the system described by the differencial equation (the elasticity of a material or the mass of a pendulum, etc...), while the arbitrary constants give diferent solutions depending on the initial conditions of the system (for example, the initial phase of a mass connected to a spring).

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