v 2.12

$${2 \pi f(t - \frac{z}{v}) = \omega (t - \frac{z}{v})=\omega t-\frac{2\pi f}{v}z = \omega t - \frac{2\pi }{vT} z= \omega t -\frac{2\pi }{\lambda} z= 2 \pi (\frac{t}{T} - \frac{z}{\lambda})}$$