diff --git a/calculus-derivatives-with-python.ipynb b/calculus-derivatives-with-python.ipynb
index bfffcaa..db215a2 100644
--- a/calculus-derivatives-with-python.ipynb
+++ b/calculus-derivatives-with-python.ipynb
@@ -382,7 +382,7 @@
             "cell_type": "markdown",
             "metadata": {},
             "source": [
-                "What this does, is tells us the slope of the line tangent to the graph at the point $(a, f(a))$. Suppose we have the function $f(x) = x^2$, and we want to know the slope of the tangent line at $x = 2$.  We can define a function as usual, and a function for the derivative. We can use these to write an equation of the line tangent to the graph of the function at this point.  "
+                "What this does is tells us the slope of the line tangent to the graph at the point $(a, f(a))$. Suppose we have the function $f(x) = x^2$, and we want to know the slope of the tangent line at $x = 2$.  We can define a function as usual, and a function for the derivative. We can use these to write an equation of the line tangent to the graph of the function at this point.  "
             ]
         },
         {