\magnification=\magstep1

$$
{a} \quad = \quad { {v^2}\over{r} } \quad = 
              \quad  {  {G M} \over {r^2}  }
$$


$$
r \quad = \quad d \thinspace \tan{\theta} \quad \simeq \quad d \thinspace \theta 
$$

$$
M \quad = \quad {{v^2 r} \over {G} }
$$


\bye
