code: function() {
  
        // acosh(c) = log(c + sqrt(c^2 - 1))
  
        var res = this['acos']();
        if (res['im'] <= 0) {
          var tmp = res['re'];
          res['re'] = -res['im'];
          res['im'] = tmp;
        } else {
          var tmp = res['im'];
          res['im'] = -res['re'];
          res['re'] = tmp;
        }
        return res;
      }
docs: Calculate the complex asinh
  
  @returns {Complex}