cacos, cacosf, cacosl - complex arc cosine

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ cacos(), cacosf(), cacosl()                                                 │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       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))

       /* Link with "-lm" */

       #include <complex.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.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);
       }

       glibc 2.1.  C99, POSIX.1-2001.

       Math library (libm, -lm)

       cacos, cacosf, cacosl - complex arc cosine

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

Linux man-pages 6.9.1                              2024-06-15                                           cacos(3)

       C11, POSIX.1-2008.

#include<complex.h>doublecomplexcacos(doublecomplexz);floatcomplexcacosf(floatcomplexz);longdoublecomplexcacosl(longdoublecomplexz);