\magnification=\magstep2


$$
   {d\vec{L}\over{dt} }  =  \vec{\tau} 
$$


$$
   d\vec{L} \thinspace  =  \thinspace  \vec{\tau} \thinspace {dt}
$$

$$
   ( \vec{L_f} - \vec{L_i} ) \thinspace  =  
            \thinspace  \vec{\tau} \thinspace {dt}
$$


$$
    \vec{L_f} \thinspace  =  \thinspace  \vec{L_i} \thinspace + 
                                 \thinspace \vec{\tau} \thinspace {dt}
$$

$$\eqalign{
\left| dL \right| \thinspace &= \thinspace
                     ( {\rm \ radius \ } ) ( {\rm \ angle \ } ) \cr
                             &= \thinspace 
                     \quad ( \left| L_i \right| ) \qquad ( d \phi ) \cr
 \left | \tau \thinspace dt \right|     &= \thinspace 
                     \quad ( \left| L_i \right| ) \qquad ( d \phi ) \cr
}
$$

$$
   \left|  { d \phi } \over { dt } \right|  =  
$$

\bye 
