.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL
.\"
.TH CATAN 3 2007-12-26 "" "Linux Programmer's Manual"
.SH NAME
catan, catanf, catanl \- complex arc tangents
.SH SYNOPSIS
.B #include <complex.h>
.sp
.BI "double complex catan(double complex " z );
.br
.BI "float complex catanf(float complex " z );
.br
.BI "long double complex catanl(long double complex " z );
.sp
Link with \fI\-lm\fP.
.SH DESCRIPTION
The
.BR catan ()
function calculates 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].
.LP
One has:
.nf

    catan(z) = 1 / 2i clog((1 + iz) / (1 \- iz))
.fi
.SH "CONFORMING TO"
C99.
.SH "SEE ALSO"
.BR ccos (3),
.BR clog (3),
.BR complex (7)