Eulerangle within certain zone of degrees

Hi guys,

I've got a pie template, and on this pie template there's a little zone (50 degrees width) moving around. The player controls and arrow on this pie plate, and has to press a button once the arrow is within the zone.

The problem I'm having however, is that eulerangles only range from 0 - 360. This means whenever the zone is at 350 degrees, the left side is actually at 15 degrees while the right side is at 325 degrees. Because of this I can't figure out if the arrow is within the zone. Any ideas on how to tackle this problem?