====== ccos ======
<code c>
double complex ccos(double complex z);
</code>

==== description of ccos ====
calculate the complex cosine

<code c>
#include <stdio.h>
#include <complex.h>

int main( void )
{

   long double complex zlong=4.2 + I*2.34;
   double complex zdouble=(double complex)zlong;

   double result;

   result = ccos(zdouble);
   printf("ccos(%f + I*%f) = %f\n", creal(zdouble), cimag(zdouble), result);
   return 0;
}

</code>

===== output of ccos c example =====
    ccos(4.200000 + I*2.340000) = -2.568370