Cfrgtkky

I'm using the package geometry to customize my document. I specify the geometry I want using newgeometry after a title that I will make later.

If I do that using the code below, the first page is ok, but after executing newpage the document seems to forget the geometry I want to use for the whole document, and then this new page is not centered with respect to the first page anymore.

Is there a way to use my defined geometry with newgeometry in the page right after newpage?

documentclass{book}



usepackage[T1]{fontenc}

usepackage[utf8]{inputenc}

usepackage[a4paper]{geometry}



usepackage{sidenotes} % Notes in the margin

usepackage{comment}



begin{comment} 



    begin{marginfigure}

    includegraphics[width=marginparwidth]{example-image-a}%

    caption{This is in the margin.}%

    end{marginfigure}



end{comment}



usepackage{graphicx}



usepackage{fancyhdr}

pagestyle{fancy}

renewcommand{headrulewidth}{0.4pt}

renewcommand{footrulewidth}{0.4pt}



begin{document}

    % Future title here

    newgeometry{

        a4paper,

        centering, 

        layoutwidth=20cm,

        layouthoffset = -1cm,

        layoutheight = 34cm,

        layoutvoffset = -2.5cm

    }



    setcounter{chapter}{-1}

    chapter{Basic concepts}

    thispagestyle{fancy}

    section{Multiply two numbers}



    When we have to numbers $ a $ and $ b $ and we want to multiply them we have

    [

    acdot b = c

    ]

    where $ c $ is the result of multiplying $ a $ and $ b $

    newpage

    a

end{document}

If you are going to use the same geometry for the whole document, you don't need to call newgeometry command in the biggining of the document but call usepackage command of geometry with the options you wish to have.

Also, as mentioned in the comment, you need oneside documentclass.

So, Something like this could work for you (adjust the numbers to fit your needs):

documentclass[a4paper,oneside]{book}



usepackage[T1]{fontenc}

usepackage[utf8]{inputenc}

usepackage[centering, 

        layoutwidth=20cm,

        layouthoffset = -0.5cm,

        layoutheight = 34cm,

        layoutvoffset = -2.5cm]{geometry}



usepackage{sidenotes} % Notes in the margin

usepackage{comment}



begin{comment} 



    begin{marginfigure}

    includegraphics[width=marginparwidth]{example-image-a}%

    caption{This is in the margin.}%

    end{marginfigure}



end{comment}



usepackage{graphicx}



usepackage{fancyhdr}

pagestyle{fancy}

renewcommand{headrulewidth}{0.4pt}

renewcommand{footrulewidth}{0.4pt}



begin{document}

    % Future title here



    setcounter{chapter}{-1}

    chapter{Basic concepts}

    thispagestyle{fancy}

    section{Multiply two numbers}



    When we have to numbers $ a $ and $ b $ and we want to multiply them we have

    [

    acdot b = c

    ]

    where $ c $ is the result of multiplying $ a $ and $ b $

    newpage

    noindent a

end{document}