With Atto text editor and equation editor enabled (using MathJax filter)

Select the Equation editor Advanced tab, The matrix (last) button does not display properly and inserts:

\left| \begin

{matrix} a_1 & a_2 \ a_3 & a_4 \end{matrix}

\right|

rather than:

\left| \begin

{matrix} a_1 & a_2 \ \ a_3 & a_4 \end{matrix}

\right|

Needs to be fixed in the settings,php file where the \ \ denoting the matrix new line needs to be \\\\. Presumably an escaping issue.

Also, consider adding a few more useful default expressions.

Full set of Greek Symbols

\alpha
\beta
\gamma
\delta
\epsilon
\zeta
\eta
\theta
\iota
\kappa
\lambda
\mu
\nu
\xi
\omicron
\pi
\rho
\sigma
\tau
\upsilon
\phi
\chi
\psi
\omega

{\rm A} {\rm B}

\Gamma
\Delta

{\rm E} {\rm Z} {\rm H}

\Theta

{\rm I} {\rm K}

\Lambda

{\rm M} {\rm N}

\Xi

{\rm O}

\Pi

{\rm P}

\Sigma

{\rm T}

\Upsilon
\Phi

{\rm X}

\Psi
\Omega

Some additional Advanced expressions

\frac

{a}{b}
a_b
a^b
a_b^c
\sqrt{a}

\sqrt[n]

{a}
\log
\log_{10}
\log_e
\ln
e^x
\cos
\sin
\tan
\left(a\right)
\left[a\right]
\left{a\right}
\left|a\right|
\overline{a}

\underline

{a}