[Tex/LaTex] How to correctly indent a paragraph

horizontal alignmentindentation

I want to indent a paragraph so that each new line of it starts from the same position as shown below:

 line 1
 line 2
 line 3

The LaTeX code below generates paragraph indented as follows:

  line 1
line 2
line 3

How can it be corrected?

LaTeX:

\section*{\hspace{150pt} Motivation}
\hspace{10pt}\begin{normalsize}
tagging conventions to define the general structure of a document (such as    
article, book, and letter), to stylise text throughout a document (such as 
bold and italic), and to add citations and cross-referencing. A TeX 
distribution such as TeXlive or MikTeX is used to produce an output file 
(such as PDF or DVI) suitable for printing or digital distribution.

Best Answer

I give it a try:

Standard Behaviour

The standard paragraph shows an indentation in the first line and no space between paragraphs (\parskip is zero).

\documentclass{article}

\usepackage{blindtext}

\begin{document}

\blindtext

\blindtext

\end{document}

Standard Document Class Solution

You can use the parskip package (CTAN link) to solve your problem.

From the documentation:

Package to be used with any document class at any size. It produces the following Paragraph Layout:

Zero Parindent and non-zero Parskip. The stretchable glue in \parskip helps LaTeX in finding the best place for page breaks.

In addition, the package adjusts the skips between list items.

This package is no more than quick fix; the ‘proper’ way to achieve effects as far-reaching as this is to create a new class. An example class is to be found in the ntgclass set: artikel3.cls

The koma-script bundle classes and the memoir class all provide similar functionality, and their respective documentation files discuss the pros (such as they are) and cons of this approach.

\documentclass{article}

% new package
\usepackage{parskip}

\usepackage{blindtext}

\begin{document}

\blindtext

\blindtext

\blindlist{itemize}

\end{document}

Bad Solution: Manually Change the Lengths

Important for you is that the package parskip takes care of other things too. Sometimes you see people manually changing the parameters like \setlength{\parindent}{0em} and \setlength{\parskip}{1em} but this is considered bad because it also could change the distance between items in lists and so on. But I am not an expert here.

Alternative Solution: KOMA Approach

There are the so called KOMA-Script (CTAN link) document classes (in contrast to the standard document classes like article and book).

They offer a document class option called parskip which also "takes care of everything".

\documentclass[parskip]{scrartcl}

\usepackage{blindtext}

\begin{document}

\blindtext

\blindtext

\blindlist{itemize}

\end{document}

PS: I don't get the

\section*{\hspace{150pt} Motivation}
\hspace{10pt}\begin{normalsize}

part of your code.

Related Solutions

[Tex/LaTex] Indent an entire paragraph / section

I would use the adjustwidth environment from the changepage package:

\begin{adjustwidth}{<left margin>}{<right margin>}
...
\end{adjustwidth}

The entire contents of adjustwidth are indented from the left margin by <left margin> and from the right margin by <right margin>. Here's a minimal working example:

\documentclass{article}
\usepackage{changepage}% http://ctan.org/pkg/changepage
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\begin{document}
\section{Some section title inserted here with some custom gibberish}
\begin{adjustwidth}{2.5em}{0pt}
\lipsum[1]
\end{adjustwidth}
\lipsum[2-5]
\end{document}

Adjustwidth of first paragraph

The standard article document class indents the section title by 2.5em.

Edit: After seeing your minimal working example (MWE), I would suggest using the enumitem package to provide the appropriate margin alignment in your "problem" set. Below is a revised version of your MWE with the correct redefinition.

\documentclass[10pt,a4paper]{article}
\usepackage[hmargin=3cm,vmargin=3.5cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage[norsk]{babel}
\usepackage{amsmath}

\usepackage{enumitem}
\usepackage[hidelinks]{hyperref}
\usepackage[dvipsnames*,svgnames]{xcolor}

\newcommand{\oppgave}[2]{\section*{Oppgave #1 {\normalfont\normalsize (#2 poeng)}
\addcontentsline{toc}{section}{Oppgave #1}}}

\newcommand{\del}[1]{%
  \item \addcontentsline{toc}{subsection}{#1)}
}

\newlist{deloppg}{enumerate}{2}
\setlist[deloppg]{label=\arabic*),leftmargin=*,itemsep=5pt}

\begin{document}

\tableofcontents

\newpage

\section*{Fasitsvar til regneoppgaver}
\addcontentsline{toc}{section}{Fasitsvar til regneoppgaver}

\newpage

\noindent
\phantomsection
\addcontentsline{toc}{section}{{\color{red}\Large{Del 1}}}
\fcolorbox{black}{LightSteelBlue}{%
  \parbox[t][1.25cm][c]{\textwidth}{%
    \begin{center}
      \textbf{Del 1 \\Uten hjelpemiddler}
    \end{center}%
  }%
}

\oppgave{1}{18}

\begin{enumerate}[leftmargin=*,labelsep=2em,label=\alph*)]
\del{a} \label{1a}
  Vis at den deriverte til funksjonen $O(x) = \dfrac{500}{x} + 8x^2 $ er
  %
  \begin{align*}
    O'(x) = \frac{ -500 + 16x^3 }{x^2}
  \end{align*}
  %
\del{b} Deriver funksjonene \\ 
\begin{deloppg}
  \item  $ f(x) = 3  \ln(2x)       $ 
  \item  $ g(x) = 3x \cdot e^{x^2} $ \aa 
\end{deloppg}
%
\vspace{5mm}
%
\del{c} Vi har gitt polynomfunksjonen $f(x)=x^3 - 3x^2 - 13x + 15$
\begin{deloppg}
  \item Vis at $f(1)=0$. Bruk polynomdivisjon til å faktorisere $f(x)$  i førstegradsfaktorer
  \item Løs ulikheten $f(x)\leq 0$
\end{deloppg} 
%
\vspace{5mm}
%
\del{d}
  Mengden av lava som spruter ut per time ved et vulkanutbrudd kan 
  tilnærmet beskrives ved et funksjonsuttrykk $f(x)$. Funksjonsverdiene 
  er målt i tonn, og $t$ er antall timer etter begynnelsen av utbruddet. \\ \\ Du får vite at: $f(0)=300, \qquad f'(10)=0 \qquad \textnormal{og} \qquad         f''(10) = -10$\\ \\ Hva kan du si om vulkanutbruddet på grunnlag av disse opplysningene? 
\end{enumerate}
\end{document}

Enumitem defintion for problems

Looking at your code there could be some improvements made. However, since the MWE might only cover a portion of what you're after, I merely tried to make things work the way you want them to.

[Tex/LaTex] How to define the size of paragraph indent

Set the \parindent length to the desired value:

\setlength\parindent{1cm}

A complete example using your code:

\documentclass[12pt]{article}

\setlength\parindent{1cm}

\begin{document}

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor 
incididunt ut labore et dolore magna aliqua. 

Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip 
ex ea commodo consequat. 

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore 
eu fugiat nulla pariatur. 

\end{document}

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