diff --git a/lib/extramath.js b/lib/extramath.js
new file mode 100644
index 0000000..4678989
--- /dev/null
+++ b/lib/extramath.js
@@ -0,0 +1,50 @@
+// lib/extramath.js
+// https://github.com/gnh1201/welsonjs
+
+function DTM() {
+    this.data = [];
+    this.terms = [];
+
+    this.add = function(s) {
+        var w = s.trim().split(/\s+/);
+        for (var i = 0; i < w.length; i++) {
+            if (this.terms.indexOf(w[i]) < 0) this.terms.push(w[i]);
+        }
+        this.data.push(w);
+    };
+
+    this.toDTM = function() {
+        var dtm = [];
+        for (var i = 0; i < this.data.length; i++) {
+            var dt = [];
+            for (var k = 0; k < this.terms.length; k++) {
+                dt.push(this.data[i].indexOf(this.terms[k]) < 0 ? 0 : 1);
+            }
+            dtm.push(dt);
+        }
+        return dtm;
+    };
+}
+
+function cosineSim(A, B) {
+    var dotproduct = 0;
+    var mA = 0;
+    var mB = 0;
+    for (i = 0; i < A.length; i++) { // here you missed the i++
+        dotproduct += (A[i] * B[i]);
+        mA += (A[i] * A[i]);
+        mB += (B[i] * B[i]);
+    }
+    mA = Math.sqrt(mA);
+    mB = Math.sqrt(mB);
+    var similarity = (dotproduct) / ((mA)*(mB)) // here you needed extra brackets
+    return similarity;
+}
+
+exports.DTM = DTM;
+exports.cosineSim = cosineSim;
+
+exports.VERSIONINFO = "ExtraMath module (extramath.js) version 0.0.1";
+exports.AUTHOR = "catswords@protonmail.com";
+exports.global = global;
+exports.require = global.require;