LaTeX公式

buffer_convertlyxformatixl896.lyx ended unexpectedly, which means that it is probably corrupted
文件路径中有中文名哦

Missing character: There is no Ⅰ in font futb8t!
Missing character: There is no Ⅱ in font futb8t!
Ⅰ、Ⅱ在2.1.4以前的版本用都没有问题。可能需要设置字体

LaTeX不直接支持显示大小写罗马数字, 但是可以通过自定义命理来实现.
定义新的命令\rmnum，\Rmnum，用来显示大小写罗马数字
用法：\rmnum{数字}，\Rmnum{数字}
\makeatletter
\newcommand{\rmnum}[1]{\romannumeral #1}
\newcommand{\Rmnum}[1]{\expandafter\@slowromancap\romannumeral #1@}
\makeatother
在文章的导言区加入上面四行, 然后就可以在正文中使用命令\rmnum{数字},Rmnum{数字}来分别显示大小写罗马数字

解决方程组未知数对齐的问题：
More Math Into LaTeX, 5th_[2016],
6.1.2 Three exceptions (P169)
--------------------------------------------------------------------------------------------
+ or − are binary operations when preceded and followed by a symbol or an empty group, {}.
\begin{alignat*}{2}
(A + B C)x &{}+{} &C &y = 0,\\
Ex &{}+{} &(F + G) &y = 23.
\end{alignat*}
we use the empty groups, {}, to tell L A T E X that the second + in line 1 and the first + in
line 2 of the formula are binary operations.
\begin{alignat}{2}
(A + B C)x &+{} &C &y = 0,\\
Ex &+{} &(F + G) &y = 23.
\end{alignat}
\begin{alignat}{4}
a_{11}x_1 &+ a_{12}x_2 &&+ a_{13}x_3 &&
&&= y_1,\\
a_{21}x_1 &+ a_{22}x_2 && &&+ a_{24}x_4
&&= y_2,\\
a_{31}x_1 & &&+ a_{33}x_3 &&+ a_{34}x_4
&&= y_3.
\end{alignat}
--------------------------------------------------------------------------------------------
“align at several places”
The alignat environment is very important for typing systems of equations.
--------------------------------------------------------------------------------------------
An align is a table-like structure, and & is a column separator. The thing is that the columns in an align are rlrlrlrlrl..., that is, every other column is right aligned and left aligned.
questions/159723/what-does-a-double-ampersand-mean-in-latex
format: rlrlrlrlrl
\[
\left\{
\begin{alignedat}{8}
2x_{1} & +{} & x_{2} & -{} &5x_{3} & +{} & x_{4} &=&8, \\
x_{1} & -{} &3 x_{2} & & & -{} &6x_{4} &=&-9, \\
& &2 x_{2} & -{} &x_{3} & +{} &2x_{4} &=&-5, \\
x_{1} & +{} &4 x_{2} & -{} &7x_{3} & +{} &6x_{4} &=&0.
\end{alignedat}
\right.
\]

不常用的数学符号：\DeclareMathOperator{\arccot}{arccot} 或者直接用\mathop{arccot}

Latex beamer "Madrid"，如果不要地下的标题，可修改beamerthemeMadrid.sty，注释掉“\useoutertheme{infolines}”。也可根据爱好修改beamerouterthemeinfolines.sty