diff --git a/machine_learning/custom_feature_map.ipynb b/machine_learning/custom_feature_map.ipynb
index 73b870d..2e07ddf 100644
--- a/machine_learning/custom_feature_map.ipynb
+++ b/machine_learning/custom_feature_map.ipynb
@@ -231,7 +231,7 @@
     "    Returns:\n",
     "        double: the mapped value\n",
     "    \"\"\"\n",
-    "    coeff = x[0] if len(x) == 1 else functools.reduce(lambda m, n: m * n, np.pi - x)\n",
+    "    coeff = x[0] if len(x) == 1 else functools.reduce(lambda m, n: m * n, np.sin(np.pi - x))\n",
     "    return coeff"
    ]
   },
@@ -509,7 +509,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.4"
+   "version": "3.7.6"
   }
  },
  "nbformat": 4,