Some detail optimization

.vscode/settings.json

@@ -0,0 +1,12 @@
+{
+    "python.testing.unittestArgs": [
+        "-v",
+        "-s",
+        ".",
+        "-p",
+        "test_*.py"
+    ],
+    "python.testing.pytestEnabled": false,
+    "python.testing.nosetestsEnabled": false,
+    "python.testing.unittestEnabled": true
+}

Exercise.02.ipynb

@@ -0,0 +1,32 @@
+{
+ "metadata": {
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": 3
+  },
+  "orig_nbformat": 2
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2,
+ "cells": [
+  {
+   "source": [
+    "## congruence class of a modulo\n",
+    "\n",
+    "Let a and n be integers with n > 0. The congruence class of a modulo n, denoted\n",
+    "$[a]n$, is the set of all integers that are congruent to a modulo n; i.e.,\n",
+    "$[a]n = {z ∈ Z | a − z = kn\\: for\\: some\\: k ∈ Z}$ ."
+   ],
+   "cell_type": "markdown",
+   "metadata": {}
+  }
+ ]
+}