CACOS(3) | Library Functions Manual | CACOS(3)

# NAME

`cacos`, `cacosf`, `cacosl` — complex circular arc cosine

# SYNOPSIS

Math Library (libm, -lm)
`#include <complex.h>`

double complex
`cacos`(double complex z);

float complex
`cacosf`(float complex z);

long double complex
`cacosl`(long double complex z);

# DESCRIPTION

The `cacos`(), `cacosf`() and `cacosl`() functions compute the complex circular arc cosine of z.

For all complex floating-point numbers z,

    cacos(z) = Pi/2 - casin(z).

# RETURN VALUES

The `cacos`(), `cacosf`() and `cacosl`() functions return the complex circular arc cosine of z with unbounded imaginary part, and real part in the interval [0, Pi].

# SEE ALSO

casin(3), catan(3)

# STANDARDS

The `cacos`(), `cacosf`() and `cacosl`() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

June 7, 2025 | Debian