Make formula consistent.

git-svn-id: https://svn.dealii.org/trunk@19391 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-37/doc/intro.dox b/deal.II/examples/step-37/doc/intro.dox
index 99b6276b6290d42821234759c70026b933d41e26..1ec698b4a8f51471740b6ca171d52cb632b6c934 100644 (file)
--- a/deal.II/examples/step-37/doc/intro.dox
+++ b/deal.II/examples/step-37/doc/intro.dox
@@ -109,7 +109,7 @@ In order to find out how we can write a code that performs a matrix-vector
 product, but does not need to store the matrix elements, let us start at
 looking how some finite-element related matrix $A$ is assembled:
 @f{eqnarray*}
-A = \sum_{j=1}^{\mathrm{n,cells}} P_\mathrm{cell,{loc-glob}}^T A_\mathrm{cell}
+A = \sum_{\mathrm{cell}=1}^{\mathrm{n,cells}} P_\mathrm{cell,{loc-glob}}^T A_\mathrm{cell}
 P_\mathrm{cell,{loc-glob}}.
 @f}
 In this formula, the matrix $P_\mathrm{cell,{loc-glob}}$ is a permutation
@@ -123,7 +123,7 @@ If we are to perform a matrix-vector product, we can hence use that
 @f{eqnarray*}
 y &=& A\cdot x = \left(\sum_{\text{cell}=1}^{\mathrm{n,cells}} P_\mathrm{cell,{loc-glob}}^T
 A_\mathrm{cell} P_\mathrm{cell,{loc-glob}}\right) \cdot x\\
-&=& \sum_{j=1}^{\mathrm{n,cells}} P_\mathrm{cell,{loc-glob}}^T
+&=& \sum_{\mathrm{cell}=1}^{\mathrm{n,cells}} P_\mathrm{cell,{loc-glob}}^T
 A_\mathrm{cell} x_\mathrm{cell},
 @f}
 where $x_\mathrm{cell}$ is the values of <i>x</i> at the degrees of freedom