Refactor code for improved readability and consistency across multiple Jupyter notebooks

- Added missing commas in various print statements and function calls for better syntax.
- Reformatted code to enhance clarity, including breaking long lines and aligning parameters.
- Updated function signatures to use float type for sigma parameters instead of int for better precision.
- Cleaned up comments and documentation strings for clarity and consistency.
- Ensured consistent formatting in plotting functions and data handling.

L3/Calculs Numériques/Interpolation.ipynb

@@ -527,7 +527,7 @@
     "    \"\"\"Build the Vandermonde matrix for points x.\"\"\"\n",
     "    size = x.shape[0]\n",
     "    M = np.reshape(x, (size, 1))\n",
-    "    power = list(range(0, size))\n",
+    "    power = list(range(size))\n",
     "    return M**power\n",
     "\n",
     "\n",