[join]

для примера:

var n=0;
var x=1;
var plusY='';
var minusY='';

matanaliz(50);

function matanaliz(total){
  var num = '';
  for( var i=1; i <= total; i++ ){
    n=i;
	num = (Math.abs(Math.sin(n*x) - Math.cos(n/x)));
	(num >= 0) ? (plusY += (num + '; (n='+n+',x='+x+') ' + '\t\n')) : (minusY += num + '; (n='+n+',x='+x+') ' + '\t\n');
  }
  console.log('plusY: '+plusY);
  console.log('minusY: '+minusY);
};