gnuplottex размер шрифта

set terminal epslatex standalone color colortext size 6cm,9cm header "\\usepackage[8pt]{extsizes}"

\documentclass[12pt,a4paper]{article}

\usepackage{tikz}
\usepackage{gnuplot-lua-tikz}
\usepackage{gnuplottex}
\usepackage{caption,subcaption}

\begin{document}
\begin{figure}
  \begin{subfigure}[b]{.5\linewidth}
    \begin{gnuplot}
      set terminal tikz color size 6cm,4cm fontscale 0.5
      set key box top left
      set key width 5
      set sample 1000
      set xr [-5:5]
      set yr [-1:1]
      set xlabel '$x$'
      set ylabel '$y$'
      plot sin(x) w l lc 1 t '$\sin(x)$',\
      cos(x) w l lc 2 t '$\cos(x)$',\
      tan(x) w l lc 3 t '$\tan(x)$',\
      tanh(x) w l lc 4 t '$\tanh(x)$'
    \end{gnuplot}
    \caption{A figure}
  \end{subfigure}
  \begin{subfigure}[b]{.5\linewidth}
    \begin{gnuplot}
      set terminal tikz color size 6cm,4cm fontscale 0.8
      set key box top left
      set key width 5
      set sample 1000
      set xr [-5:5]
      set yr [-1:1]
      set xlabel '$x$'
      set ylabel '$y$'
      plot sin(x) w l lc 1 t '$\sin(x)$',\
      cos(x) w l lc 2 t '$\cos(x)$',\
      tan(x) w l lc 3 t '$\tan(x)$',\
      tanh(x) w l lc 4 t '$\tanh(x)$'
    \end{gnuplot}
    \caption{Another figure}
  \end{subfigure}
  \caption{Two figures}
\end{figure}
\end{document}