diff --git a/notebooks/Preliminaries_Numpy_Pandas/Jupyter Notebook - Introduction Numpy and Pandas.ipynb b/notebooks/Preliminaries_Numpy_Pandas/Jupyter Notebook - Introduction Numpy and Pandas.ipynb
index 17afb7b40bd1228b640585cf0bab0cb4719f0da9..00809b7846b9dbe89721c0323a4b6220f437aeaf 100644
--- a/notebooks/Preliminaries_Numpy_Pandas/Jupyter Notebook - Introduction Numpy and Pandas.ipynb	
+++ b/notebooks/Preliminaries_Numpy_Pandas/Jupyter Notebook - Introduction Numpy and Pandas.ipynb	
@@ -11,7 +11,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 182,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [
     {
@@ -45,7 +45,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 183,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -87,7 +87,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 184,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -1603,7 +1603,7 @@
     "### NumPy's `dot` function\n",
     "\n",
     "You may sometimes see NumPy's `dot` function in places where you would expect a `matmul`. \n",
-    "It turns out that the results of `dot` and `matmul` are the same if the matrices are two dimensional.\n",
+    "It turns out that the results of `dot` and `matmul` are the same if the arrays are two dimensional.\n",
     "\n",
     "So these two results are equivalent:"
    ]
@@ -2049,12 +2049,18 @@
     "$$\n",
     "\\begin{align}\n",
     "\\sin(90) & =1 \\\\\n",
-    "\\cos(90) & = 1\\\\\n",
+    "\\cos(90) & = 0\\\\\n",
     "\\end{align}\n",
     "$$\n",
     "\n",
     "\n",
-    "$$T_r=\n",
+    "$$T_r\n",
+    "=\n",
+    "\\left(\\begin{array}{rrr} \n",
+    "\\cos(\\theta) & \\sin(\\theta) & 0 \\\\ \n",
+    "-\\sin(\\theta) & \\cos(\\theta) & 0 \\\\ \n",
+    "0 & 0 & 1 \\\\ \n",
+    "\\end{array}\\right)=\n",
     "\\left(\\begin{array}{rrr} \n",
     "0 & 1 & 0 \\\\ \n",
     "-1 & 0 & 0 \\\\ \n",