Undefined Control Sequence while using \itemize in beamer. If I change it from beamer to article, it works

Question

\documentclass{beamer}
\usepackage{bookmark}
\usepackage[utf8]{inputenc}
\usepackage{multicol}
\usepackage{graphicx}
\begin{document}
.\\
\vspace{3.5cm}
\centering{\Huge\textbf{DELIMITERS}}

\newpage
.\vspace{1cm}
\\ A \textbf{Delimiter} act as a symbol that acts
logically like parenthesis, with a pair of delimiters enclosing an expression.

They can only be used in Math mode.\\The delimiters recognized by \textit{LaTeX} includes:
\newpage
.\\
\vspace{1cm}
Delimiters in Formula should be big enough to fit around the formula they delimit (for example around arrays).To obtain "Stretchable" delimiters type \verb+\left +or \verb+\right+ command

For Example by writing :\hspace{10pt}
\verb+\left( + $x^2$ \verb+ \right) + \\we will get output as: \hspace{10pt}
$\left(x^2 \right)$
\newpage
.\\
\vspace{1cm}
The two \verb+\left+ and \verb+\right+ commands must come in matching pair but the matching delimiters need not to be the same.\vspace{0.5cm}
\begin{minipage}{0.5\textwidth}
$x+y+z=\left(\begin{array}{c}a\\ b\end{array}\right[$\\
\end{minipage}\begin{minipage}{0.5\textwidth}
\verb^ $x+y+z=\left(\begin{array}^\hspace{3pt}
\verb^{c}a\\ b\end{array}\right[$^
\end{minipage}\vspace{0.5cm}
Some formula require delimiter on one side only.So we can hide a delimiter by adding "." after the \verb+\left+ or \verb+\right+ command.\\
\vspace{1cm}
\begin{minipage}{0.5\textwidth}
$x=\left\{\begin{array}{ll}
y  &  \mbox{if $y>0$}\\
x+y   & \mbox{otherwise}
\end{array}
\right[$
\end{minipage}\begin{minipage}{0.5\textwidth}
\verb%$x=\left\{\begin{array}{ll}%
\verb%\mbox{if$y>0$}\\%
\verb%& \mbox{otherwise}\end{array}%
\verb% \right[% 
\end{minipage}

\newpage
.\\
\vspace{1cm}
{\huge \textbf{EXAMPLE}}
\begin{flushleft}
\verb+$\left[\begin{array}{ccc}x_1 & x_2 &+\\ \verb+x_3\\y_1 & y_2 & y_3\\ z_1 & z_2 &+\\ \verb+z_3\end{array}\right]$+\\ \vspace{1cm}
  \textbf{  Will show output as:-}
  $$\left[\begin{array}{ccc}
   x_1     & x_2  &  x_3 \\
    y_1    & y_2  &   y_3  \\
    z_1    &  z_2 &   z_3
   \end{array}
   \right]$$
   \end{flushleft}


\newpage
.\\
\vspace{3.5cm}
\centering\textbf{\Huge ELLIPSES}
\newpage
.\\
\vspace{1cm}
\textbf{Ellipses} are small dots used in typesetting Mathematical Equations to denote continuation of something. 
\begin{itemize}
 \item abab\\
 \item jdhd
\end{itemize}
nsns
\newpage
.\\
\vspace{.8cm}
{\huge \textbf{EXAMPLE}}
\begin{flushleft}
\verb+$\left[ \begin{array}{cccc}+
\verb+\mathbf{x{_11}}&  \mathbf{x_{12}}& + \verb+\mathbf{\cdots}&+
\verb+\mathbf{x_{1n}}& \\+
\verb+\mathbf{x_{21}}& \mathbf{$x_{22}}$+
\verb+ & \mathbf{\cdots}& \mathbf{x_{2n}} \\+
\verb+\mathbf{\vdots}&  \mathbf{vdots}&+
\verb+\mathbf{\ddots}& \mathbf{\vdots}\\+
\verb+\mathbf{x_{m1}}&  mathbf{ x_{m2}}+
\verb+ & mathbf{\cdots}&+ 
\verb+\mathbf{x_{mn}} \end{array}\right]$+\\
\vspace{0.5cm}
\textbf{Will show output as:}
$\left[\begin{array}{cccc}
   \mathbf{X_{11}} & \mathbf{X_{12}} &  \mathbf{\cdots}  & \mathbf{X_{1n}} \\
  \mathbf{X_{21}}   & \mathbf{X_{22}}    & \mathbf{\cdots}      &  \mathbf{X_{2n}}   \\
  \mathbf{\vdots}   & \mathbf{\vdots}    &  \mathbf{\ddots}    & \mathbf{\vdots}    \\
   \mathbf{X_{m1}}  & \mathbf{X_{m2}}    & \mathbf{\cdots}     & \mathbf{X_{mn}}
\end{array}        \right]$
\end{flushleft}
\end{document}

Welcome to TeX.SX! There are currently no frame environments in your beamer document but several \newpage commands. You might want to correct that. Also, what's the purpose of .\\? — leandriis, Oct 19 '19 at 13:23
beamer is intended for presentation, not to write plain text as in article. You should devide your document body on frames! — Zarko, Oct 19 '19 at 13:25
For \verb to work correctly inside of a beamer frame, you will need thefragileoption (\begin{frame}[fragile]`) — leandriis, Oct 19 '19 at 13:27
For showing longer sections of verbatim code, you might be interested in using either the listings or the minted package. Probably, using tcolorbox could also be useful. With this package (in combination iwth one of the before mentioned) you can show input code and compiled output in comparison without havig to repeat the code twice. — leandriis, Oct 19 '19 at 13:45
Off topic: the code .\\ \vspace{...} at the beginning of a new page is better input as \vspace*{...} with the dimension adjusted as appropriate. (The starred version of \vspace doesn't disappear at the top of a page.) — barbara beeton, Oct 19 '19 at 18:50

leandriis · Answer 1 · 2019-10-19T14:08:24.003

Here is the last page of your example document converted into beamer. In the first frame, I have not changed your use of \verb while I have relaced it in the second frame with the lstlisting environment from the listings package. In the third frame, I have used tcolorbox in combination with its listing library in order to get the verbatim code as well as the output without having to type the same code twice:

\documentclass{beamer}
\usepackage{listings}
\usepackage{tcolorbox}
\tcbuselibrary{listings}


\begin{document}

\begin{frame}[fragile]
{\huge \textbf{EXAMPLE}}
\begin{flushleft}
\verb+$\left[ \begin{array}{cccc}+
\verb+\mathbf{x{_11}}&  \mathbf{x_{12}}& + \verb+\mathbf{\cdots}&+
\verb+\mathbf{x_{1n}}& \\+
\verb+\mathbf{x_{21}}& \mathbf{$x_{22}}$+
\verb+ & \mathbf{\cdots}& \mathbf{x_{2n}} \\+
\verb+\mathbf{\vdots}&  \mathbf{vdots}&+
\verb+\mathbf{\ddots}& \mathbf{\vdots}\\+
\verb+\mathbf{x_{m1}}&  mathbf{ x_{m2}}+
\verb+ & mathbf{\cdots}&+ 
\verb+\mathbf{x_{mn}} \end{array}\right]$+\\
\vspace{0.5cm}
\textbf{Will show output as:}
$\left[\begin{array}{cccc}
   \mathbf{X_{11}} & \mathbf{X_{12}} &  \mathbf{\cdots}  & \mathbf{X_{1n}} \\
  \mathbf{X_{21}}   & \mathbf{X_{22}}    & \mathbf{\cdots}      &  \mathbf{X_{2n}}   \\
  \mathbf{\vdots}   & \mathbf{\vdots}    &  \mathbf{\ddots}    & \mathbf{\vdots}    \\
   \mathbf{X_{m1}}  & \mathbf{X_{m2}}    & \mathbf{\cdots}     & \mathbf{X_{mn}}
\end{array}        \right]$
\end{flushleft}
\end{frame}

\begin{frame}[fragile]
\frametitle{Example}
\begin{lstlisting}[breaklines=true]
$\left[\begin{array}{cccc}
   \mathbf{X_{11}} & \mathbf{X_{12}} & \mathbf{\cdots} & \mathbf{X_{1n}}  \\
   \mathbf{X_{21}} & \mathbf{X_{22}} & \mathbf{\cdots} &  \mathbf{X_{2n}} \\
   \mathbf{\vdots} & \mathbf{\vdots} & \mathbf{\ddots} & \mathbf{\vdots}  \\
   \mathbf{X_{m1}} & \mathbf{X_{m2}} & \mathbf{\cdots} & \mathbf{X_{mn}}
\end{array}\right]$
\end{lstlisting}

\textbf{Will show output as:}
$\left[\begin{array}{cccc}
   \mathbf{X_{11}} & \mathbf{X_{12}} &  \mathbf{\cdots}  & \mathbf{X_{1n}} \\
  \mathbf{X_{21}}   & \mathbf{X_{22}}    & \mathbf{\cdots}      &  \mathbf{X_{2n}}   \\
  \mathbf{\vdots}   & \mathbf{\vdots}    &  \mathbf{\ddots}    & \mathbf{\vdots}    \\
   \mathbf{X_{m1}}  & \mathbf{X_{m2}}    & \mathbf{\cdots}     & \mathbf{X_{mn}}
\end{array}        \right]$
\end{frame}

\begin{frame}[fragile]
\frametitle{Example}
\begin{tcblisting}{colback=white,colframe=gray}
$\left[\begin{array}{cccc}
   \mathbf{X_{11}} & \mathbf{X_{12}} & \mathbf{\cdots} & \mathbf{X_{1n}}  \\
   \mathbf{X_{21}} & \mathbf{X_{22}} & \mathbf{\cdots} &  \mathbf{X_{2n}} \\
   \mathbf{\vdots} & \mathbf{\vdots} & \mathbf{\ddots} & \mathbf{\vdots}  \\
   \mathbf{X_{m1}} & \mathbf{X_{m2}} & \mathbf{\cdots} & \mathbf{X_{mn}}
\end{array}\right]$
\end{tcblisting}
\end{frame}

\end{document}

Unrelated to the beamer question itself but more regarding the contents of this specific frame: Instead of repeatedly typing \mathbf{...}, I'd use \boldmath. I'd also replace \left[\begin{array}{cccc} with \begin{bmatrix} as shown in the following example:

\boldmath{\[\begin{bmatrix}
   X_{11} & X_{12} & \cdots & X_{1n}  \\
   X_{21} & X_{22} & \cdots &  X_{2n} \\
   \vdots & \vdots & \ddots & \vdots  \\
   X_{m1} & X_{m2} & \cdots & X_{mn}
\end{bmatrix}\]}

Undefined Control Sequence while using \itemize in beamer. If I change it from beamer to article, it works

1 Answers1