cacos, cacosf, cacosl − complex arc cosine

#include <complex.h>

double complex cacos(double complex z);

float complex cacosf(float complex z);

long double complex cacosl(long double complex z);

The cacos() function calculates the complex acos(). If y = cacos(z), then z = ccos(y). The real part of y is chosen in the interval [0,pi].

One has cacos(z) = -i clog(z+csqrt(z*z-1)).

C99

clog(3), ccos(3)