.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL
.\"
.TH CACOS 3 2008-08-11 "" "Linux Programmer's Manual"
.SH NAME
cacos, cacosf, cacosl \- complex arc cosine
.SH SYNOPSIS
.B #include <complex.h>
.sp
.BI "double complex cacos(double complex " z );
.br
.BI "float complex cacosf(float complex " z );
.br
.BI "long double complex cacosl(long double complex " z );
.sp
Link with \fI\-lm\fP.
.SH DESCRIPTION
The
.BR cacos ()
function calculates the complex arc cosine of
.IR z .
If \fIy\ =\ cacos(z)\fP, then \fIz\ =\ ccos(y)\fP.
The real part of
.I y
is chosen in the interval [0,pi].
.LP
One has:
.nf

    cacos(z) = \-i clog(z + csqrt(z * z \- 1))
.fi
.SH VERSIONS
These functions first appeared in glibc in version 2.1.
.SH "CONFORMING TO"
C99.
.SH "SEE ALSO"
.BR ccos (3),
.BR clog (3),
.BR complex (7)