man-pages/man3/catanh.3

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.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL
.\"
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.TH CATANH 3 2007-12-26 "" "Linux Programmer's Manual"
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.SH NAME
catanh, catanhf, catanhl \- complex arc tangents hyperbolic
.SH SYNOPSIS
.B #include <complex.h>
.sp
.BI "double complex catanh(double complex " z );
.br
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.BI "float complex catanhf(float complex " z );
.br
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.BI "long double complex catanhl(long double complex " z );
.sp
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Link with \fI\-lm\fP.
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.SH DESCRIPTION
The
.BR catanh ()
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function calculates the complex arc hyperbolic tangent of
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.IR z .
If \fIy\ =\ catanh(z)\fP, then \fIz\ =\ ctanh(y)\fP.
The imaginary part of
.I y
is chosen in the interval [\-pi/2,pi/2].
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.LP
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One has:
.nf
catanh(z) = 0.5 * clog((1 + z) / (1 \- z))
.fi
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.SH "CONFORMING TO"
C99.
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.SH "SEE ALSO"
.BR atanh (3),
.BR cabs (3),
.BR cimag (3),
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.BR complex (7)