Which programming language should I use?

#include <iostream>
#include <complex>

using namespace std;

int main ()
{
    complex<double> z1, z2, z3;
    z1 = complex<double> (1.0, 2.0);
    z2 = complex<double> (3.0, 4.0);
    cout << "z1 = " << z1 << endl;
    cout << "z2 = " << z2 << endl;
    z3 = z1 + z2;
    cout << "Sum = " << z3 << endl;
    z3 = z1 * z2;
    cout << "Product = " << z3 << endl;
    return 0;
}

#include <iostream>
#include <complex>
#include <cmath>

using namespace std;

// my attempt at a complex-valued acos() function

complex<double> acos (const complex<double>& x)
{
    const complex<double> eye = complex<double>(0,1);
    const complex<double> one = 1;
    return -eye*log(x + eye*sqrt(one - x*x));
}

int main ()
{
    complex<double> z = 2;
    cout << acos(z) << endl;  // this outputs "(0,1.31696)"
    return 0;
}

/* File complex_itrig.h */
/* Uart's complex inverse trig library */

#include <complex>
typedef std::complex<double> cmplx;
const cmplx _I = cmplx(0.0,1.0);
const cmplx _1 = cmplx(1.0,0.0);

cmplx atan(cmplx x) {
       return 0.5*_I*( log(_1 - _I*x) - log(_1 + _I*x) );
       }

cmplx asin(cmplx x) {
      return atan( x / sqrt(_1-x*x) );
      }
             
cmplx acos(cmplx x) {
      return atan( sqrt(_1-x*x) / x );
      }

cmplx acosh(cmplx x) {
      return -_I * acos(x);
      }

cmplx asinh(cmplx x) {
      return -_I * asin(_I*x);
      }

cmplx atanh(cmplx x) {
      return -_I * atan(_I*x);
      }