# CASIN

NAME

SYNOPSIS

DESCRIPTION

VERSIONS

ATTRIBUTES

CONFORMING TO

SEE ALSO

COLOPHON

## NAME

casin, casinf,
casinl − complex arc sine

## SYNOPSIS

**#include
<complex.h>**

**double
complex casin(double complex** *z***); **

float complex casinf(float complex *z***); **

long double complex casinl(long double complex
*z***);**

Link with
*−lm*.

## DESCRIPTION

The
**casin**() function calculates the complex arc sine of
*z*. If *y = casin(z)*, then
*z = csin(y)*. The real part of *y* is
chosen in the interval [−pi/2,pi/2].

One has:

casin(z) =
−i clog(iz + csqrt(1 − z * z))

## VERSIONS

These functions
first appeared in glibc in version 2.1.

## ATTRIBUTES

For an
explanation of the terms used in this section, see
**attributes**(7).

## CONFORMING TO

C99.

## SEE ALSO

**clog**(3),
**csin**(3), **complex**(7)

## COLOPHON

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part of release 3.53 of the Linux *man-pages* project.
A description of the project, and information about
reporting bugs, can be found at
http://www.kernel.org/doc/man−pages/.