Because in this case, "infinity" is treated as the name of a scoped attribute (EL variable). Since you haven't defind such an attribute, the output is empty. There are no constants for "infinity" or "NaN" in EL---and I very much doubt you'd need them in any real Web app either.
Charles Lyons (SCJP 1.4, April 2003; SCJP 5, Dec 2006; SCWCD 1.4b, April 2004)
Author of OCEJWCD Study Companion for Oracle Exam 1Z0-899 (ISBN 0955160340 / AmazonAmazon UK )