small edits

module2/exo1/toy_notebook_en.ipynb

@@ -4,7 +4,13 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "#  On the computation of $\\pi$\n",
+    "#  On the computation of $\\pi$"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
     "##  Asking the maths library\n",
     "\n",
     "My computer tells me that $\\pi$ is *approximatively*"
@@ -32,8 +38,8 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Buffon’s needle\n",
-    "Applying the method of [Buffon’s needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__"
+    "## Buffon's needle\n",
+    "Applying the method of [Buffon's needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__"
    ]
   },
   {
@@ -65,7 +71,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "##  Using a surface fraction argument\n",
+    "## Using a surface fraction argument\n",
     "A method that is easier to understand and does not make use of the sin function is based on the fact that if $X\\sim U(0,1)$ and $Y\\sim U(0,1)$, then $P[X^2+Y^2\\leq 1] = \\pi/4$ (see [\"Monte Carlo method\" on Wikipedia](https://en.wikipedia.org/wiki/Monte_Carlo_method)). The following code uses this approach:"
    ]
   },