\magnification=\magstep2


$$
 a_y \quad = \quad { {d^2 y} \over {d t^2}} \quad = 
$$


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

$$
  x(t) \quad = \quad  A \cos \left( \omega t \right) 
$$


\bye
