\begin{figure}[H]
	\pgfplotsset{
		axis lines=middle,
		axis line style={->},
		xmin=0,
		xticklabels=empty,
		xtick=\empty,
		ymin=-1,
		ymax=1,
		yticklabels=empty,
		ytick=\empty,
		samples=200,
		every axis plot post/.append style={very thick},
		clip=true,
	}% end of common axis set
	\begin{tikzpicture}
		\begin{axis}% 1. plot
			[
			domain=0:4*pi,
			xmax=pi,
			yscale=0.5,
			xlabel={$\lambda=\frac{2L}{1}$}
			]
			\addplot[red] {(sin(deg(x+pi))/2)*-1};
		\end{axis}
		\begin{axis}% 2. plot

\begin{figure}
	\centering
	\begin{minipage}[.5\textwidth]
		\centering
		\import{graphs/}{energylevels}
		\captionof{Three first energy levels allowed for a particle in a potential box}
		\label{fig:energylevels}
	\end{minipage}%
	\begin{minipage}[.5\textwidth]
		\centering
		\import{graphs/}{wavefunctions}
		\captionof{Three first wave functions for a given system}
		\label{fig:wavefunctions}
	\end{minipage}
\end{figure}
\begin{figure}