Is the \begin{align} function available for the MaTeX package?
Use aligned
from amsmath (I do not think align
or align*
works in Matex)
Needs["MaTeX`"]
SetOptions[MaTeX,"Preamble"->{"\\usepackage{amssymb,amsmath,latexsym,amsfonts,amsthm}"}]
Then
MaTeX["
\\begin{aligned}
V&= \\int_0^H dV\\\\
&= \\int_0^H A'\\,dh\\\\
&= \\int_0^H\\frac{Ah^2}{H^2}\\,dh\\\\
&= \\frac{A}{H^2}\\left|\\frac{h^3}{3}\\right|_0^H\\\\
&= \\frac{A}{H^2}\\cdot\\frac{H^3}{3}\\\\
&= \\frac{1}{3}AH
\\end{aligned}
"]
Gives
Second example
MaTeX["
\\begin{aligned}
\\int_0^r 2\\pi r\\,dr &= 2\\pi \\int_0^r r\\,dr \\\\
&= 2\\pi\\bigg\\vert_0^r \\frac{r^2}{2} \\\\
&= \\bigg(2\\pi \\frac{r^2}{2}\\bigg)-\\bigg(2\\pi \\frac{0^2}{2}\\bigg) \\\\
&= \\frac{2\\pi r^2}{2} \\\\
&= \\boldsymbol{\\pi r^2}
\\end{aligned}
"]
Gives
MaTeX interprets TeX commands in inline math mode. Only those commands work that are allowed in inline math mode.
As @Nasser said, in this case use aligned
instead of align
(and make sure that the amsmath
package is loaded—it is in the default "BasePreamble"
option value).
This is discussed both on the webpage you linked to, and the builtin documentation. Please check the documentation (in particular the Possible Issues section) when encountering problems like this. It has answers to the most common questions.