diff --git a/4. Jupyter - kalkulator symboliczny.ipynb b/4. Jupyter - kalkulator symboliczny.ipynb
index f9e20fe..9d015d7 100644
--- a/4. Jupyter - kalkulator symboliczny.ipynb	
+++ b/4. Jupyter - kalkulator symboliczny.ipynb	
@@ -1068,7 +1068,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from mpl_toolkits.mplot3d import Axes3D"
+    "from mpl_toolkits.mplot3d import Axes3D\n",
+    "from numpy import arange"
    ]
   },
   {
@@ -1942,7 +1943,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.1"
+   "version": "3.9.0"
   },
   "varInspector": {
    "cols": {