   I should know that!
  Today, much to my chagrin, I discovered that I no longer knew how to project a point onto a line. Back to the geometry texts with me, I suppose.What bits of knowledge you really should have known have you suddenly found yourself missing?   
  That pencil-and-paper square root algorithm that looks similar to division.[edit]This one.  Didn't know it could do higher roots, though.[Edited by - Flarelocke on May 30, 2006 1:50:07 AM];  Subject-verb agreement pwned me today.   