Changed caption of Figure 8.1 to improve clarity.

Seems like either 'coincide' or 'are concident' would work here.

public/textbook/applicationsOfDifferentiation.tex

@@ -104,7 +104,7 @@ \section{L'H\^{o}pital's Rule}
         \end{axis}
 \end{tikzpicture}
 \caption{A plot of $f(x)=\sin(x)$ and $g(x) = x$. Note how the tangent
-  lines for each curve are coincide at $x=0$.}
+  lines for each curve are coincident at $x=0$.}
 \label{example:sinx and x}
 \end{marginfigure}