Wave equation

{tag=Important partial differential equation}
{wiki}

Describes perfect lossless waves on the surface of a string, or on a water surface.

Uniqueness: https://math.stackexchange.com/questions/1113622/uniqueness-of-solutions-to-the-wave-equation

As mentioned at: https://math.stackexchange.com/questions/579453/real-world-application-of-fourier-series/3729366#3729366[] from <solving partial differential equations with the Fourier series> citing https://courses.maths.ox.ac.uk/node/view_material/1720[], analogously to the <heat equation>, the wave linear equation can be be solved nicely with <separation of variables>.
