Replace \atan by \text{atan} because the former is apparently not part of MathJAX.

diff --git a/examples/step-7/doc/intro.dox b/examples/step-7/doc/intro.dox
index 726d570fffa7cc05a94f5b37534e7ee6cc22dac4..f70cf04e0ea2f2525722b173aa9db08772582813 100644 (file)
--- a/examples/step-7/doc/intro.dox
+++ b/examples/step-7/doc/intro.dox
@@ -191,7 +191,7 @@ denote $\bar u|_{\Gamma_1}=g_1$ and ${\mathbf n}\cdot \nabla\bar u|_{\Gamma_2}=g
   $f = -\Delta \bar u + \bar u$ is. Since the derivative of an exponential
   is relatively straightforward to compute, the choice above satisfies this
   requirement, whereas a function of the kind
-  $\bar u(\mathbf x) = \atan\left(\|\mathbf x\|^{\|\mathbf x\|}\right)$
+  $\bar u(\mathbf x) = \text{atan}\left(\|\mathbf x\|^{\|\mathbf x\|}\right)$
   would have presented greater difficulties.
   (ii) You *don't* want $\bar u$ be a polynomial of low degree. That is
   because if you choose the polynomial degree of your finite element