carg.3: Add introductory sentence explaining what these functions calculate

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man3/carg.3 b/man3/carg.3
index dbecd90c7ac839afb11a260f638efbfb11dd81a3..3c65eeda98073f34f980f160d2155295d2b8e2db 100644 (file)
--- a/man3/carg.3
+++ b/man3/carg.3
@@ -18,6 +18,10 @@ carg, cargf, cargl \- calculate the complex argument
 .sp
 Link with \fI\-lm\fP.
 .SH DESCRIPTION
+These functions calculate the complex argument (also called phase angle) of
+.IR z ,
+with a branch cut along the negative real axis.
+
 A complex number can be described by two real coordinates.
 One may use rectangular coordinates and gets