\begin{equation}
\begin{aligned}
E\left ( \varepsilon _{n}\right )
&=E\left ( v_{n}t_{n} \right )+E\left ( X_{n}^{\left ( v_{n} \right )} \right )\\
&=E\left ( v_{n}t_{n} \right )+E\left [ E\left ( X_{n}^{\left ( v_{n} \right )}\mid v_{n} \right ) \right ]\\
&=\frac{R}{1-R}\cdot \frac{t_{1}}{a^{n-1}}+\frac{1}{1-R} \int_{0}^{t_{n}}tdF\left ( a^{n-1}t \right )\\
&=\frac{1}{\left ( 1-R \right )a^{n-1}}\int_{0}^{t_{1}}\left ( 1-F\left ( t \right ) \right )dt
\end{aligned}
\end{equation}

$\sigma$

\alpha

\begin{eqnarray}
e^x &\approx& 1+x+x^2/2! + \\
   && {}+x^3/3! + x^4/4! + \\
   && + x^5/5!
\end{eqnarray}

try

\begin{align}
\text{e}^{i\pi}=-1
\end{align}

try
$\alpha$

$$\text{e}^{i\pi}=-1$$

$\text{e}^{i\pi}=-1$

failure...

Very good! 要等会儿才能看到啊

很好啊！

very good ,thank you very much

\[$\beta$\]

试一下 可以么 $\sigma$

还没用到，呵呵

试试 \[a+b=c\]

不会用，以后再看吧

great!
\[
\intop_{0}^{\infty}f\left\{ \frac{\sqrt{\alpha^{\beta}\ln\Gamma_{t}}}{\sum_{0}^{\infty}x_{t}}\right\} \textrm{d}x\leq\mathbb{R}^{+}
\]

长见识了，谢谢！

\[\mathds{F}-(x)=\sum^{N}_{i=1}{\mathca{P}(i^2)}\]

\[E=Mc^2\]

   \[\mathds{P}\{M(t)\in dm,B(t)\in db\}=\frac{2(2m-b)}{t\sqrt{2\pi t}}
   \exp\left\{-\frac{(2m-b)^2}{2t}\right\}dm\ db,\ m>0,b<m.\]

$\sum_{i=1}^{n}i=frac{n(n+1)}{2}$

再试一下啊$\sum_{i=0}^{n}i^2=\frac{n(n+1)(2n+1)}{6}$

Thank you so much for your sharing with us.

Safari显示异常啊显示异常啊显示异常啊

有些不是很好理解。

mathtype怎么获取latex代码呀？

$\left(X^{\prime}X\right)^{-1}X^\prime Y$

可以设置复制粘贴的选项的，就在设置里面吧，很久没有用这个了，不知改版了没