From: David Wells <wellsd2@rpi.edu>
Date: Sat, 25 Jun 2016 23:27:34 +0000 (-0400)
Subject: Fix some matrix coefficients in the step-25 intro.
X-Git-Tag: v8.5.0-rc1~952^2~2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4653c8e02ead6aebc143f97dd393110b72d6c363;p=dealii.git

Fix some matrix coefficients in the step-25 intro.

The above formula has the correct sign on N. Additionally, the Laplace
matrix here is missing the coefficients.
---

diff --git a/examples/step-25/doc/intro.dox b/examples/step-25/doc/intro.dox
index 03ae995ab2..f1a5761816 100644
--- a/examples/step-25/doc/intro.dox
+++ b/examples/step-25/doc/intro.dox
@@ -176,9 +176,10 @@ i.e. $N_{ij}(f,g) = \left( \cos\left[ \theta f + (1-\theta) g\right]\varphi_i,
 What solvers can we use for the first equation? Let's look at the matrix we
 have to invert:
 @f[
-  (M+k^2\theta^2(A-N))_{ij} = 
-  \int_\Omega (1+k^2\theta^2 \cos \alpha) 
-  \varphi_i\varphi_j \; dx+\int_\Omega \nabla\varphi_i\nabla\varphi_j \; dx,
+  (M+k^2\theta^2(A + N))_{ij} =
+  \int_\Omega (1+k^2\theta^2 \cos \alpha)
+  \varphi_i\varphi_j \; dx
+  + k^2 \theta^2 \int_\Omega \nabla\varphi_i\nabla\varphi_j \; dx,
 @f]
 for some $\alpha$ that depends on the present and previous solution. First,
 note that the matrix is symmetric. In addition, if the time step $k$ is small