How do I create a frame around an entire section, so that it doesn't eat up my table?

Question

used mdframe for 1st and it worked, and in the second it eats it up.

Here is the latex code:

\documentclass [10pt]{ article}
\usepackage[utf8]{ inputenc}
\usepackage[croatian]{babel}
\usepackage{amsfonts}
\usepackage{color}
\usepackage{amsmath}
\usepackage{mdframed}
\DeclareMathOperator{\tg}{tg}
\DeclareMathOperator{\ctg}{ctg}
\title{LaTeX vježbe-5}
\author{Dino Luinović}
\date{30.10.2017}

\begin{document}
    \maketitle
    \pagenumbering{gobble}
    \newpage
    \pagenumbering{arabic}
    \newtheorem{zadatak}{Zadatak}[section]
    \begin{mdframed}
    \section{Derivacija}
    \subsection{Tehnika deriviranja}

    \textbf{Definicija:} Neka je $f:I\rightarrow\mathbb{R}$ funkcija, $I\subseteq\mathbb{R}$ otvoreni interval i $c\in I$.Kažemo da je $f$ derivabilna u $c$ ako postoji\\
    \begin{equation}\label{derlim}
    \lim_{x \to c}\frac{f(x)-f(c)}{x-c}\\
    \end{equation}
    i taj limes označimo s $f'(c).$

    \begin{zadatak}
        Koristeći definiciju $\left( {\color{red}\ref{derlim}} \right)$, 
        odredite derivaciju funkcije $ f(x)= \cos(x).$  
    \end{zadatak}
    \textbf{Rješenje:}\\
    \begin{align*}
    f'(c) & = \lim_{x \to c}\frac{f(x)-f(c)}{x-c}\\
    & = \lim_{x \to c}\frac{\sin(x)-\sin(c)}{x-c}\\
    & = \lim_{x \to c}\frac{-2\sin(\frac{x+c}{2})\sin(\frac{x-c}{2})}{x-c}\\
    & = -\sin c
    \end{align*}\\

    \begin{itemize}
        \item[DZ:] Neka je $f(x)= \ln\left(\frac{x^2}{x-1}\right)$. Odredite:
        \item[(a)] domenu funkcije $f$
        \item[(b)] intervale monotonosti i ekstreme.
    \end{itemize}

\end{mdframed}

    \newpage
    \begin{mdframed}

    \section{Integral}
    \subsection{Tablica Integrala}
    \begin{table}[h]
        \centering
        \caption{Integrali}
        \label{tab1}
        \begin{tabular}{|l | l| c|}
            \hline
            $\int\ dx = x + C$ & $\int\frac{\,dx}{\cos^2 x}=\tg x + C$\\
            \hline
            $\int\ x^a {\,dx}=\frac{x^{a+1}}{a+1} + \ +C (a \neq -1)$
            &$\int\frac{\,dx}{\sin^2 x}=-\ctg x+\ C$ \\
            \hline
        \end{tabular}
    \end{table}

    Tablica $\left( {\color{red}\ref{tab1}} \right)$ prikazuje integrale nekih funkcija.

\end{mdframed}



    \section{Red}
    \subsection{Taylorovi redovi}
    U ovom području se zadaju naredbe za treću sekciju.
    \section{Matrice}
    A ovdje pišemo naredbe za sekciju Matrice.


\end{document}