NAME

cacos — complex inverse cosine function

SYNOPSIS

double complex
cacos(double complex z);

long double complex
cacosl(long double complex z);

float complex
cacosf(float complex z);

cacos(z) computes the inverse cosine of the complex floating-point number z, with branch cuts outside the interval [-1,1] along the real axis.

cacos() returns values in a strip of the complex plane with unbounded imaginary part, and real part in the interval [0, Pi].

For all complex floating point numbers z, cacos(conj(z)) = conj(cacos(z)).

The conjugate symmetry of cacos() is used to abbreviate the specification of special values.

cacos(±0 + 0i) returns Pi/2 - 0i.

cacos(±0 + NaN i) returns Pi/2 + NaN i.

cacos(x + inf i) returns Pi/2 - inf i, for finite x.

cacos(x + NaN i) returns NaN + NaN i, for finite nonzero x.

cacos(-inf + yi) returns Pi - inf i, for finite positive-signed y.

cacos(inf + yi) returns 0 - inf i, for finite positive-signed y.

cacos(-inf + inf i) returns 3Pi/4 - inf i.

cacos(inf + inf i) returns Pi/4 - inf i.

cacos(±inf + NaN i) returns NaN + inf i.

cacos(NaN + yi) returns NaN + NaN i, for finite y.

cacos(NaN + inf i) returns NaN - inf i.

cacos(NaN + NaN i) returns NaN + NaN i.

The cacos() function conforms to ISO/IEC 9899:2011.