diff --git a/Notebooks/Chap03/3_4_Activation_Functions.ipynb b/Notebooks/Chap03/3_4_Activation_Functions.ipynb
index d9277e2a..b08449a3 100644
--- a/Notebooks/Chap03/3_4_Activation_Functions.ipynb
+++ b/Notebooks/Chap03/3_4_Activation_Functions.ipynb
@@ -4,7 +4,7 @@
   "metadata": {
     "colab": {
       "provenance": [],
-      "authorship_tag": "ABX9TyOu5BvK3aFb7ZEQKG5vfOZ1",
+      "authorship_tag": "ABX9TyPmra+JD+dm2M3gCqx3bMak",
       "include_colab_link": true
     },
     "kernelspec": {
@@ -185,7 +185,7 @@
         "The ReLU isn't the only kind of activation function.  For a long time, people used sigmoid functions.  A logistic sigmoid function is defined by the equation\n",
         "\n",
         "\\begin{equation}\n",
-        "f[h] = \\frac{1}{1+\\exp{[-10 z ]}}\n",
+        "f[z] = \\frac{1}{1+\\exp{[-10 z ]}}\n",
         "\\end{equation}\n",
         "\n",
         "(Note that the factor of 10 is not standard -- but it allow us to plot on the same axes as the ReLU examples)"