Mirror image of the neg symbol?

Question

Is there a mirror symbol for the $\neg$ symbol, or a symbol like $\vdash$ without the bottom part of the vertical line? I couldn't find it. Thanks.

Answer 1

\llcorner from amsmath or \niv from nath, amongst others. Just look in the usual places.

Answer 2

If you want something with the exact same proportions, you could rotate the original symbol

\documentclass{article}
\usepackage{graphicx}
\newcommand{\rotatedneg}{\rotatebox[origin=c]{180}{\ensuremath\neg}}
\begin{document}
\[
\neg \rotatedneg \vdash
\]
\end{document}