documentclass{report}
usepackage{tikz}
begin{document}
    fbox{tikz{%
        fill[red!20] (0,0) to[in=210,out=30] (10,0) -- (10,1) -- (0,1) -- cycle;
        }}

    bigskip

    fbox{tikz{%
        fill[red!20] (0,0) -- (10,0) -- (10,1) -- (0,1) -- cycle;
        }}
end{document}