数学符号 - 不出现

Question

我对数学符号有疑问。\leg 无法显示在 PDF 中。

\documentclass[12pt,a4paper,notitlepage]{report}
\usepackage{polski}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[top=2cm, bottom=2cm, left=3cm, right=3cm]{geometry}
\usepackage{newpxtext, newpxmath}
\usepackage{longtable}
\usepackage{enumitem}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}


\usepackage{makeidx}
\usepackage{graphicx}

\usepackage{pgf,tikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\definecolor{cqcqcq}{rgb}{0.7529411764705882,0.7529411764705882,0.7529411764705882}

\usepackage{blkarray}
\newcommand\eqcomment[1]{\fbox{\makebox[4cm]{#1}}}

\usepackage{float}

\newcommand{\subscript}[2]{$#1 _ #2$}

\DeclareSymbolFont{symbolsC}{U}{ntxsyc}{m}{n}
\DeclareMathSymbol{\simp}{\mathrel}{symbolsC}{74}