cacos(3) - f38

1cacos(3)                   Library Functions Manual                   cacos(3)
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NAME

6       cacos, cacosf, cacosl - complex arc cosine
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LIBRARY

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <complex.h>
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14       double complex cacos(double complex z);
15       float complex cacosf(float complex z);
16       long double complex cacosl(long double complex z);
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DESCRIPTION

19       These  functions  calculate  the  complex  arc cosine of z.  If y = ca‐
20       cos(z), then z = ccos(y).  The real part of y is chosen in the interval
21       [0,pi].
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23       One has:
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25           cacos(z) = -i * clog(z + i * csqrt(1 - z * z))
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ATTRIBUTES

28       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
29       tributes(7).
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31       ┌────────────────────────────────────────────┬───────────────┬─────────┐
32       │Interface                                   │ Attribute     │ Value   │
33       ├────────────────────────────────────────────┼───────────────┼─────────┤
34       │cacos(), cacosf(), cacosl()                 │ Thread safety │ MT-Safe │
35       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

38       C11, POSIX.1-2008.
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HISTORY

41       glibc 2.1.  C99, POSIX.1-2001.
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EXAMPLES

44       /* Link with "-lm" */
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46       #include <complex.h>
47       #include <stdio.h>
48       #include <stdlib.h>
49       #include <unistd.h>
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51       int
52       main(int argc, char *argv[])
53       {
54           double complex z, c, f;
55           double complex i = I;
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57           if (argc != 3) {
58               fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]);
59               exit(EXIT_FAILURE);
60           }
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62           z = atof(argv[1]) + atof(argv[2]) * I;
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64           c = cacos(z);
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66           printf("cacos() = %6.3f %6.3f*i\n", creal(c), cimag(c));
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68           f = -i * clog(z + i * csqrt(1 - z * z));
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70           printf("formula = %6.3f %6.3f*i\n", creal(f), cimag(f));
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72           exit(EXIT_SUCCESS);
73       }
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