diff --git a/04_Regularisation.ipynb b/04_Regularisation.ipynb
index 21a3a9a..ab24513 100644
--- a/04_Regularisation.ipynb
+++ b/04_Regularisation.ipynb
@@ -86,9 +86,9 @@
     "Hence, the gradient of the cost w.r.t parameter $w_i$ is given as follows:\n",
     "\n",
     "(5) $\n",
-    "\\begin{align*}\\frac{\\partial E^n}{\\partial w_i} &= \\frac{\\partial (E^n_{\\text{train}} + \\beta_{L_2} E_{L_2}) }{\\partial w_i} \n",
+    "\\begin{align*}\\frac{\\partial E^n}{\\partial w_i} &= \\frac{\\partial (E^n_{\\text{train}} + \\beta_{L_2} \frac{1}[2} E^n_{L_2}) }{\\partial w_i} \n",
     "  = \\left( \\frac{\\partial E^n_{\\text{train}}}{\\partial w_i}  + \\beta_{L_2} \\frac{\\partial\n",
-    "      E_{L_2}}{\\partial w_i} \\right) \n",
+    "      \frac{1}{2}E^n_{L_2}}{\\partial w_i} \\right) \n",
     "  = \\left( \\frac{\\partial E^n_{\\text{train}}}{\\partial w_i}  + \\beta_{L_2} w_i \\right)\n",
     "\\end{align*}\n",
     "$\n",