\magnification=\magstep1

$$
 \tan(\theta) \quad = \quad { {R} \over {L} }
$$

$$
 \theta \ ({\rm in\ radians})  \quad \simeq \quad { {R} \over {L} }
$$

$$
 \theta \ ({\rm in\ arcsec})  \quad \simeq \quad { {R\ ({\rm in\ AU})} \over {L\ ({\rm in\ parsec})} }
$$



\bye 
