Better format a couple of formulas in step-46.

diff --git a/examples/step-46/doc/intro.dox b/examples/step-46/doc/intro.dox
index 57b3ccd6a1ad718308f80092d63d1485d78fc0fd..77305ac75a3d8317eefeb4dae7354c1699c8ad4a 100644 (file)
--- a/examples/step-46/doc/intro.dox
+++ b/examples/step-46/doc/intro.dox
@@ -78,19 +78,21 @@ multiplying from the left by a test function and integrating over the
 domain. It then looks like this: Find $y = \{\mathbf v, p,
 \mathbf u\} \in Y \subset H^1(\Omega_f)^d \times L_2(\Omega_f) \times
 H^1(\Omega_s)^d$ such that
-@f{multline*}
+@f{align*}
        2 \eta (\varepsilon(\mathbf a), \varepsilon(\mathbf v))_{\Omega_f}
        - (\nabla \cdot \mathbf a, p)_{\Omega_f}
-       - (q, \nabla \cdot \mathbf v)_{\Omega_f}
+       - (q, \nabla \cdot \mathbf v)_{\Omega_f} &
        \\
-       + (\varepsilon(\mathbf b), C \varepsilon(\mathbf u))_{\Omega_s}
+       + (\varepsilon(\mathbf b), C \varepsilon(\mathbf u))_{\Omega_s} &
        \\
        - (\mathbf b,
            (2 \eta \varepsilon(\mathbf v) + p \mathbf 1) \mathbf n)_{\Gamma_i}
-       =
+       &=
        0,
 @f}
-for all test functions $\mathbf a, q, \mathbf b$.
+for all test functions $\mathbf a, q, \mathbf b$; the first, second, and
+third lines correspond to the fluid, solid, and interface
+contributions, respectively.
 Note that $Y$ is only a subspace of the spaces listed above to accommodate for
 the various Dirichlet boundary conditions.
 
@@ -298,16 +300,16 @@ points:
 
 Let us first discuss implementing the bilinear form, which at the
 discrete level we recall to be
-@f{multline*}
+@f{align*}
        2 \eta (\varepsilon(\mathbf a_h), \varepsilon(\mathbf v_h))_{\Omega_f}
        - (\nabla \cdot \mathbf a_h, p_h)_{\Omega_f}
-       - (q_h, \nabla \cdot \mathbf v_h)_{\Omega_f}
+       - (q_h, \nabla \cdot \mathbf v_h)_{\Omega_f} &
        \\
-       + (\varepsilon(\mathbf b_h), C \varepsilon(\mathbf u_h))_{\Omega_s}
+       + (\varepsilon(\mathbf b_h), C \varepsilon(\mathbf u_h))_{\Omega_s} &
        \\
        - (\mathbf b_h,
            (2 \eta \varepsilon(\mathbf v_h) + p \mathbf 1) \mathbf n)_{\Gamma_i}
-       =
+       &=
        0,
 @f}
 Given that we have extended the fields by zero, we could in principle