Updating the notebooks

Author: AllenDowney

chapters/chap04.ipynb

@@ -346,7 +346,7 @@
  "Adding a parameter to a function is called **generalization** because it makes the function more general: with the previous version, the square is always the same size; with this version it can be any size.\n",
  "\n",
  "If we add another parameter, we can make it even more general.\n",
- "The following function draws regular polygons with a given of sides."
+ "The following function draws regular polygons with a given number of sides."
  ]
  },
  {