GEOMETRY
'(<a href="http://www.j-archive.com/media/2008-09-16_DJ_06.jpg" target="_blank">Jon of the Clue Crew shows a line segment sweeping out a circle on the monitor.</a>)  Euclid's third postulate tells us that from any line segment, a circle can be drawn with one endpoint as the center & the segment itself as this line'
radius