Question

equation for amplitude

Answer 1

x = A \sin(t - K) + b \ ,

A is the peak amplitude of the wave,
x is the oscillating variable,
t is time,
K and b are arbitrary constants representing time and displacement offsets respectively.

Answer 2

@Orbitalshawn;In your question there must be equation of wave.
BUT the amplitude relates to wave hence we may also write this equatio
\[y or x=A \times \sin (\omega \times t +\Phi)\]
where A is amplitude and \[\omega\] is angular frequency. \[\phi\] is phase constant and t is time..