====== Just a test ======

===== Seite 1 =====

$$
R = \frac{
\displaystyle{\sum_{i=1}^n (x_i-\bar{x})(y_i- 
\bar{y})}}{\displaystyle{\left[ 
\sum_{i=1}^n(x_i-\bar{x})^2 
\sum_{i=1}^n(y_i-\bar{y})^2\right]^{1/2}}}
$$

==== Seite 1b ====

$$
R = \frac{
\displaystyle{\sum_{i=1}^n (x_i-\bar{x})(y_i- 
\bar{y})}}{\displaystyle{\left[ 
\sum_{i=1}^n(x_i-\bar{x})^2 
\sum_{i=1}^n(y_i-\bar{y})^2\right]^{3/7}}}
$$

===== Seite 2 =====

\begin{align*}
e^x & = 1 + x + \frac{x^2}{2} + \frac{x^3}{6} + \cdots \\
    & = \sum_{n\geq 0} \frac{x^n}{n!}
\end{align*}