The
.BR acosh ()
function calculates the inverse hyperbolic cosine of
-\fIx\fP; that is the value whose hyperbolic cosine is \fIx\fP.
+.IR x ;
+that is the value whose hyperbolic cosine is
+.IR x .
.SH RETURN VALUE
On success, these functions return the inverse hyperbolic cosine of
.IR x .