.\" Modified 2002-07-27 by Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
-.TH ATAN 3 2008-12-02 "" "Linux Programmer's Manual"
+.TH ATAN 3 2010-09-20 "" "Linux Programmer's Manual"
.SH NAME
atan, atanf, atanl \- arc tangent function
.SH SYNOPSIS
.ad l
.BR atanf (),
.BR atanl ():
-_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
+.RS 4
+_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
+_POSIX_C_SOURCE\ >=\ 200112L;
+.br
+or
.I cc\ -std=c99
+.RE
.ad b
.SH DESCRIPTION
The