An interesting link about the earth's rotation.
<a href="http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html" target="_blank">http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html</a>
This link says that to calc the speed of rotation at a specific latitude, mult cos(latitude) * equator rotation speed (approx 1040 mph).
How is that formula derived ? I assume there is a relation between the cos(latitude) and the decreasing radius of the earth as the latitude increases.
Mike