Import from Wolfram Mathematica: Purpose of \pmb and \noindent?

pmb

DESCRIPTION \pmb command turns on poor man's bold. It works by duplicating its argument slightly offset, giving a bold effect (at least in the horizontal direction); doesn't work well for horizontal lines, like - or +.

EXAMPLE

a \pmb a \boldsymbol a

\pmb{a+b-c}\ \ a+b-c

noindent

When used at the beginning of the paragraph, it suppresses the paragraph indentation. It has no effect when used in the middle of a paragraph.

The usage of \pmb is simply absurd and likewise doublespace.

Some editing is needed if you want an acceptable result.

\documentclass[fleqn]{article}
\usepackage{amsmath, amssymb}

\newcommand{\opn}{\operatorname} % shorthand
\setlength{\mathindent}{0pt}

\begin{document}

\title{Me Salva! ITD07}
\author{Leandro Carvalho}
\date{21/06/2017}
\maketitle

\boldmath
\begin{align*}
& r_1=\sqrt{18};r_2=6\opn{Cos}[\theta ];\\
& g_1=\opn{PolarPlot}[r_1,\{\theta ,0,2 \pi \}];\\
& g_2=\opn{PolarPlot}[r_2,\{\theta ,0,2 \pi \}];\\
& \opn{Show}[\{g_1,g_2\}]\\[2ex]
& \opn{RegionPlot}[x^2+y^2<18,\{x,0,10\},\{y,0,10\},\opn{PlotStyle}\to \opn{Yellow}\\
& \opn{RegionPlot}[(x-3)^2+y^2<9,\{x,0,10\},\{y,0,10\},\opn{PlotStyle}\to \opn{Blue}\\
& \opn{RegionPlot}[x^2+y^2<18\&\&(x-3)^2+y^2<9,\{x,0,10\},\{y,0,10\}\\[2ex]
& \mathcal{R}=\opn{ImplicitRegion}[x^2+y^2<18\&\&(x-3)^2+y^2<9,\{x,y\};\\
& \opn{RegionDimension}[\mathcal{R}]\\[2ex]
& \text{\unboldmath $2$}\\
& \int _0^{\frac{\pi }{4}}\int _0^{\sqrt{18}}5 r^3 \opn{Sin}[\theta ]
    \opn{Cos}[\theta ]\,dr\,d\theta +
  \int _{\frac{\pi }{4}}^{\frac{\pi }{2}}\int _0^{6 \opn{Cos}[\theta ]}5 r^3 \opn{Sin}[\theta ]
    \opn{Cos}[\theta ]\,dr\,d\theta\\[2ex]
& \text{\unboldmath $135$}
\end{align*}

\end{document}