For example:
\begin{equation}
\delta % ok
\Delta % ok
\epsilon % ok
\Epsilon % error
\end{equation}
[Tex/LaTex] Why can I only use some capital greek letters inside the equations
greekmath-modesymbols
Related Solutions
Thanks to Mythio, I found the answer:
Use texcl=<true|false> or mathescape=<true|false> to use the inline math-evironment $\epsilon$ (see section 4.14 of the documentation)
Remove the call of the breqn package.
After the operation I get
Note that subfigure has been obsolete for several years. The official replacement is subfig. Alternatively, use subcaption. Note that the class already loads caption, so subcaption should probably be chosen.
I add a version without \left and right, which don't seem necessary (they rarely are in cases like this) and where the superscripts (n) are similar to the one for Gamma. More importantly, the two consecutive equations are together in a gather environment: two equation environments should never appear immediately after one another.
\begin{subequations}
\begin{gather}
[ \tilde{V}^{-^{(n)}} ] = [ \Gamma^{(n)} ] [ \tilde{V}^{+^{(n)}} ],
\\
[ \tilde{V}^{-\,(n)} ] = [ \Gamma^{(n)} ] [ \tilde{V}^{+\,(n)} ],
\end{gather}
\end{subequations}
In order to accommodate the split formula where you use \left and \right across lines, just remove all of them; for better clarity, some of the fences can be made \big, but not more than that. Note that multline is the environment of choice for this.
\begin{multline}
[V_m^{(n)}(z)]=[ P^{(n)} ]
\bigl( \bigl[ \exp \bigl( -j k ^{(n)} ( z-z_n) \bigr) \bigr] [ \tilde{V}^{+^{(n)}}] + \\
\bigl[ \exp \bigl( +j k ^{(n)} ( z-z_{n+1} ) \bigr) \bigr] [ \tilde{V}^{-^{(n)}} ]\bigr)
\end{multline}
Best Answer
Uppercase epsilon is E.