\input lyxtex
\narrower
\narrower

$$ {{7.2^{\circ} }\over{360^{\circ}}} = {{5000\ {\rm stadia}}\over
{{ \rm whole\ circumference}}} $$

And the circumference is $5000 \times 360/7.2 = 250000$ stadia. Since
a circumference $= 2\pi r$, the
radius of the earth must be the cirumference divided by $2\pi$, or
39800 stadia.

\vfill
\eject
\end
