/* gcc acsch.c
 * expected output: acsch(i) = 0.0000 -1.5708i
 * output on musl:  acsch(i) = -0.0000 -1.5708i
 */
#include <stdio.h>
#include <complex.h>

int main() {
  double complex arg = I;
  // acsch(x) = asinh(1 / x)
  double complex res = casinh(1.0 / arg);
  printf("acsch(i) = %.4lf %+.4lfi\n", creal(res), cimag(res));
}