code: public static function ERFC($x)
      {
          $x = Functions::flattenSingleValue($x);
  
          if (is_numeric($x)) {
              return self::erfcVal($x);
          }
  
          return Functions::VALUE();
      }
docs: ERFC.
  
  Returns the complementary ERF function integrated between x and infinity
  
  Note: In Excel 2007 or earlier, if you input a negative value for the lower bound argument,
  the function would return a #NUM! error. However, in Excel 2010, the function algorithm was
  improved, so that it can now calculate the function for both positive and negative x values.
  PhpSpreadsheet follows Excel 2010 behaviour, and accepts nagative arguments.
  
  Excel Function:
  ERFC(x)
  
  @param float $x The lower bound for integrating ERFC
  
  @return float