Manpages - cacos.3

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);

  Link with -lm.

These functions calculate the complex arc cosine of z. 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 + i * csqrt(1 - z * z))

These functions first appeared in glibc in version 2.1.

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

C99, POSIX.1-2001, POSIX.1-2008.

  /* Link with "-lm" */

  #include <complex.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <stdio.h>

  int
  main(int argc, char *argv[])
  {
      double complex z, c, f;
      double complex i = I;

      if (argc != 3) {
          fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]);
          exit(EXIT_FAILURE);
      }

      z = atof(argv[1]) + atof(argv[2]) * I;

      c = cacos(z);

      printf("cacos() = %6.3f %6.3f*i\n", creal(c), cimag(c));

      f = -i * clog(z + i * csqrt(1 - z * z));

      printf("formula = %6.3f %6.3f*i\n", creal(f), cimag(f));

      exit(EXIT_SUCCESS);
  }

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

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