My textbook gives the following for x as a function of time for a lightly damped harmonic oscillator: $$ x = Ae^{- \gamma t} \cos (\omega \, t)$$ for $\gamma = \dfrac b {2m}$.
It says this implies the amplitude follows the relationship: $$x_{max} = Ae^{-\gamma t}$$
I am not understanding where this second equation comes from. Why does the cosine term disappear if $\omega$ is a constant?