
\magnification=\magstep1


$$
y(t) \quad = \quad A \cos(\omega t + \phi)
$$

$$
y(x) \quad = \quad A \cos(k x + \phi)
$$


$$
v \quad = \quad {{\omega} \over {k}}
$$

$$
y(t) \quad = \quad A \cos(k x - \omega t + \phi)
$$



\bye
