Here are some examples:

ZENITH_ANGLE<105 && CTBCLASSLEVEL>2.5
angsep(RA,DEC,232.2,-4.9) <= 10 && (ENERGY >= 0)&&(TIME >= 239241600)
sin((DEC * #deg -(-0.09))/2.)**2 + cos(DEC * #deg)*cos(-0.09)*sin((RA * #deg -(4.05))/2.)**2 < sin(0.17/2.)**2

Note, spaces are significant, in particular spaces appear to be required around operators, otherwise the operator may be interpreted as part of the column name!

Complete documentation can be found at:

http://heasarc.nasa.gov/lheasoft/ftools/headas/rowfilter.html http://heasarc.nasa.gov/lheasoft/ftools/headas/calc_express.html