Basic Trigonometric Functions

I am trying to rotate some lines and it is not working for points less than zero. I assume it is a function of the way I'm using the trig functions, but my memory of them is a bit fuzzy, so this is a review…

var table = document.createElement("table");
document.getElementsByTagName("body").item(0).appendChild(table);

var steps = 4;
var functions = ["Math.cos(x)", "Math.sin(x)",
                 "Math.atan(Math.tan(x))",
                 "Math.floor(x/(3*Math.PI/4))",
                 "Math.atan(Math.tan(x)) + (x>=3*Math.PI/4?Math.PI:0)+ (x>3*Math.PI/2?Math.PI:0)"];
var halfRootTwo = Math.sqrt(2) / 2;

var row = document.createElement("tr");
table.appendChild(row);
var head = document.createElement("th");
head.appendChild(document.createTextNode("x"));
row.appendChild(head);
for(j = 0; j < functions.length; j++) {
  var head = document.createElement("th");
  head.innerHTML = functions[j].replace(/Math\./g, "").replace(/PI/g, "&pi;");
  row.appendChild(head);
}
  
for(i = 0; i < steps * 2; i++) {
  var row = document.createElement("tr");
  table.appendChild(row);
  var head = document.createElement("th");
  head.innerHTML = i + "&pi; / " + steps;
  row.appendChild(head);
  for(j = 0; j < functions.length; j++) {
    var elm = document.createElement("td");
    var val = eval(functions[j].replace(/x/g, "(" + i + "*Math.PI/" + steps + ")"));
    if(Math.floor(Math.abs(val) * 10000) == Math.floor(halfRootTwo * 10000)) {
      val = ((val < 0) ? "-" : "") + "&#x221A;2 / 2";
    } else if(Math.abs(val) < 0.000001) {
      val = "0";
    } else if(Math.abs(1 - Math.abs(val)) < 0.000001) {
      val = ((val < 0) ? "-" : "") + "1";
    } else if(Math.abs(val) > 999999999999) {
      val = ((val < 0) ? "-" : "") + "&#x221E;";
    } else {
      for(k = 0; k < steps * 2; k++) {
        if(Math.floor(Math.abs(val) * 10000) == Math.floor(k * Math.PI / steps * 10000)) {
          val = ((val < 0) ? "-" : "") + k + "&pi; / " + steps;
        }
      }
    }
    if(typeof(val) == "number") {
      val = Math.floor(val * 10000) / 10000;
    }
    elm.innerHTML = val;
    row.appendChild(elm);
  }
}