Define \mathbb{T} in step-3.

diff --git a/examples/step-3/doc/intro.dox b/examples/step-3/doc/intro.dox
index 32ae299667f3af0a0b5cb695050b4327e7c1333e..c2112f1ef23816fe13c56ee617b47655e71d18f9 100644 (file)
--- a/examples/step-3/doc/intro.dox
+++ b/examples/step-3/doc/intro.dox
@@ -171,7 +171,8 @@ takes to make that happen:
     \approx
     \sum_q \varphi_i(\mathbf x^K_q) f(\mathbf x^K_q) w^K_q,
   @f}
-  where $\mathbf x^K_q$ is the $q$th quadrature point on cell $K$, and $w^K_q$
+  where $\mathbb{T} \approx \Omega$ is a Triangulation approximating the domain,
+  $\mathbf x^K_q$ is the $q$th quadrature point on cell $K$, and $w^K_q$
   the $q$th quadrature weight. There are different parts to what is needed in
   doing this, and we will discuss them in turn next.
 - First, we need a way to describe the location $\mathbf x_q^K$ of quadrature