cacos(3) — Linux manual page

cacos(3)                 Library Functions Manual                cacos(3)

NAME         top

       cacos, cacosf, cacosl - complex arc cosine

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #include <complex.h>

       double complex cacos(double complex z);
       float complex cacosf(float complex z);
       long double complex cacosl(long double complex z);

DESCRIPTION         top

       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))

ATTRIBUTES         top

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

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       glibc 2.1.  C99, POSIX.1-2001.

EXAMPLES         top

       /* 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);
       }

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                       cacos(3)

Pages that refer to this page: acos(3),  ccos(3),  complex(7)

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