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+'\" t
+.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
+.\" and Copyright (C) 2011 Michael Kerrisk <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: GPL-1.0-or-later
+.\"
+.TH catan 3 2023-03-30 "Linux man-pages 6.04"
+.SH NAME
+catan, catanf, catanl \- complex arc tangents
+.SH LIBRARY
+Math library
+.RI ( libm ", " \-lm )
+.SH SYNOPSIS
+.nf
+.B #include <complex.h>
+.PP
+.BI "double complex catan(double complex " z );
+.BI "float complex catanf(float complex " z );
+.BI "long double complex catanl(long double complex " z );
+.fi
+.SH DESCRIPTION
+These functions calculate the complex arc tangent of
+.IR z .
+If \fIy\~=\~catan(z)\fP, then \fIz\~=\~ctan(y)\fP.
+The real part of y is chosen in the interval [\-pi/2,pi/2].
+.PP
+One has:
+.PP
+.in +4n
+.EX
+catan(z) = (clog(1 + i * z) \- clog(1 \- i * z)) / (2 * i)
+.EE
+.in
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.ad l
+.nh
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.BR catan (),
+.BR catanf (),
+.BR catanl ()
+T}	Thread safety	MT-Safe
+.TE
+.hy
+.ad
+.sp 1
+.SH STANDARDS
+C11, POSIX.1-2008.
+.SH HISTORY
+glibc 2.1.
+C99, POSIX.1-2001.
+.SH EXAMPLES
+.\" SRC BEGIN (catan.c)
+.EX
+/* Link with "\-lm" */
+
+#include <complex.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(int argc, char *argv[])
+{
+    double complex z, c, f;
+    double complex i = I;
+
+    if (argc != 3) {
+        fprintf(stderr, "Usage: %s <real> <imag>\en", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    z = atof(argv[1]) + atof(argv[2]) * I;
+
+    c = catan(z);
+    printf("catan() = %6.3f %6.3f*i\en", creal(c), cimag(c));
+
+    f = (clog(1 + i * z) \- clog(1 \- i * z)) / (2 * i);
+    printf("formula = %6.3f %6.3f*i\en", creal(f), cimag(f));
+
+    exit(EXIT_SUCCESS);
+}
+.EE
+.\" SRC END
+.SH SEE ALSO
+.BR ccos (3),
+.BR clog (3),
+.BR ctan (3),
+.BR complex (7)