[Tex/LaTex] symbol for proper ideal (\unlhd + \lneq)

overlayssymbols

How can I write the symbol

enter image description here

for a proper ideal?

The standard relations \leq,\subseteq both have a "proper" version \lneq,\subsetneq, but I was unable to find a "proper" version of either \unlhd or \trianglelefteq.

Any suggestions?

Best Answer

You can do by superimposing the symbols:

\documentclass[a4paper]{article}
\usepackage{amssymb}

\newcommand{\properideal}{%
  \mathrel{\ooalign{$\lneq$\cr\raise.22ex\hbox{$\lhd$}\cr}}}

\begin{document}
$I\properideal A$
\end{document}

enter image description here

A version that changes size in subscripts/superscripts; some artifacts may appear at low screen resolution.

\documentclass[a4paper]{article}
\usepackage{amsmath}
\usepackage{amssymb}

\makeatletter
\DeclareRobustCommand{\properideal}{\mathrel{\text{$\m@th\proper@ideal$}}}
\newcommand{\proper@ideal}{%
  \ooalign{$\lneq$\cr\raise.22ex\hbox{$\lhd$}\cr}%
}
\makeatother
\begin{document}
$I\properideal A_{\properideal_{\properideal}}$
\end{document}

enter image description here

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