Fix typos and example mismatches

Author: yamt

examples/Notebook/Multiple Languages, Frontends.ipynb

@@ -177,7 +177,7 @@
    "source": [
     "### install more kernels\n",
     "\n",
-    "Feel fre to experiment with other kernel, poke at the installed kernelspec folders. Use the following to list all the kernels and their locations:\n",
+    "Feel free to experiment with other kernel, poke at the installed kernelspec folders. Use the following to list all the kernels and their locations:\n",
     "\n",
     "```\n",
     "$ jupyter kernelspec list\n",

examples/Notebook/Working With Markdown Cells.ipynb

@@ -139,9 +139,9 @@
     "\n",
     "$$e^x=\\sum_{i=0}^\\infty \\frac{1}{i!}x^i$$\n",
     "\n",
-    "Use single dolars delimiter for inline math, so `$thisisinline\\int math$`  will give $this is inline\\int math$, for exampple to refer to variable within text. \n",
+    "Use single dolars delimiter for inline math, so `$thisisinline\\int math$`  will give $this is inline\\int math$, for example to refer to variable within text. \n",
     "\n",
-    "Double dollars `$$ \\int_0^\\infty f(\\phi) \\partial \\phi$$` is used for standalone formulas:\n",
+    "Double dollars `$$\\int_0^{2\\pi} f(r, \\phi) \\partial \\phi $$` is used for standalone formulas:\n",
     "\n",
     "$$\\int_0^{2\\pi} f(r, \\phi) \\partial \\phi $$\n"
    ]