+These functions are GNU extensions.
+.SH NOTES
+To see the performance advantage of
+.BR sincos (),
+it may be necessary to disable
+.BR gcc (1)
+built-in optimizations, using flags such as:
+.PP
+.in +4n
+.EX
+cc -O \-lm \-fno\-builtin prog.c
+.EE
+.in
+.SH BUGS
+Before version 2.22, the glibc implementation did not set
+.\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=15467
+.I errno
+to
+.B EDOM
+when a domain error occurred.