Wave equation:
∂²y/∂t² = (T/μ)·∂²y/∂x²

Wave speed:
c = √(T/μ)

Harmonics:
fₙ = n·c / (2L)   n=1,2,3…

Normal mode:
y(x,t) = A·sin(nπx/L)·cos(2πfₙt)