'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: GPL-1.0-or-later
.\"
.TH casin 3 (date) "Linux man-pages (unreleased)"
.SH NAME
casin, casinf, casinl \- complex arc sine
.SH LIBRARY
Math library
.RI ( libm ,\~ \-lm )
.SH SYNOPSIS
.nf
.B #include <complex.h>
.P
.BI "double complex casin(double complex " z );
.BI "float complex casinf(float complex " z );
.BI "long double complex casinl(long double complex " z );
.fi
.SH DESCRIPTION
These functions calculate the complex arc sine of
.IR z .
If
.IR "y\ =\ casin(z)" ,
then
.IR "z\ =\ csin(y)" .
The real part of
.I y
is chosen in the interval [\-pi/2,pi/2].
.P
One has:
.P
.nf
    casin(z) = \-i clog(iz + csqrt(1 \- z * z))
.fi
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR casin (),
.BR casinf (),
.BR casinl ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
glibc 2.1.
C99, POSIX.1-2001.
.SH SEE ALSO
.BR clog (3),
.BR csin (3),
.BR complex (7)