Another version of the command \triangleleft in amssymb

Question

I need the triangleleft symbol underlined like the symbol \leqslant. Thank you all!

Answer 1

Font stmaryrd provide four such symbols:

Another possibilities is font mathabx:

and font boisik (see table 135, the same document).

Source: "The Comprehensive LATEX Symbol List", Scott Pakin scott+clsl@pakin.org, 30 November 2015, page 66.

Answer 2

If you want a slanted bar, you can use picture mode:

\documentclass{article}
\usepackage{amssymb,pict2e}

\makeatletter
\newcommand{\trianglelefteqslant}{\mathrel{\mathpalette\al@tlles\relax}}

\newcommand{\al@tlles}[2]{%
  \sbox\z@{$#1\m@th\leqslant$}%
  \setlength{\unitlength}{\wd\z@}% \leqslant is essentially square
  \raisebox{-\dp\z@}{%
    \begin{picture}(1,1)
    \roundcap\roundjoin
    \polygon(0.875,1)(0.125,0.625)(0.875,0.275)
    \polyline(0.125,0.375)(0.875,0.025)
    \end{picture}%
  }%
}
\makeatother

\begin{document}

$A<\leqslant\trianglelefteqslant$

$\leqslant_{\leqslant}\trianglelefteqslant_{\trianglelefteqslant}$

\end{document}