Is there a math symbol for right(-angled) triangle?

Question

Cannot find one, all triangle symbols are equilateral triangles.

Answer 1

If you have access to Unicode fonts there is U+2BBF (⊿) RIGHT TRIANGLE

Otherwise, picture mode to the rescue:

\documentclass{article}

\usepackage{amsmath}
\def\lr{\mbox{\begin{picture}(7,10)
\put(1,0){\line(1,0){5}}
\put(1,0){\line(1,2){5}}
\put(6,0){\line(0,1){10}}
\end{picture}
}}

\def\ll{\mbox{\begin{picture}(7,10)
\put(1,0){\line(1,0){5}}
\put(6,0){\line(-1,2){5}}
\put(1,0){\line(0,1){10}}
\end{picture}
}}
\begin{document}

\begin{align}
 A &= \ll\\
 B &= \lr
\end{align}

\end{document}