Cfrgtkky

Would someone please check following code and let me know why there is different page style in pages. In fact, I want to whole pages be like the third page but I don't know why I have narrower box in first and second page.

    documentclass[12pt,a4paper]{article}

usepackage{graphicx} 

usepackage{comment}

usepackage{setspace}

doublespacing

%usepackage{amsthm,amssymb,amsmath}

usepackage{marvosym}

usepackage{MnSymbol,wasysym,boldline}

usepackage{roundbox,graphicx,framed}

usepackage{fontspec}

usepackage{fancybox}

usepackage[top=10mm, bottom=30mm, left=15mm, right=15mm,nohead]{geometry}

usepackage{array}

usepackage[font=footnotesize, labelfont=bf]{caption}

usepackage{pgfplots}

usepackage{lipsum}

usepackage{xifthen}

usepackage{tikz}

usetikzlibrary{arrows,shapes.gates.logic.US,shapes.gates.logic.IEC,calc,shapes,snakes,automata,shapes.geometric}

usepackage{xepersian}

DeclareMathSizes{14}{10}{9}{7} 

settextfont[Scale=1]{XB Niloofar.ttf}

%settextfont[Scale=1.1]{B_Nazanin.TTF}

setdigitfont[Scale=1]{Yas.TTF}

defpersianfonttitr[Scale=1]{XB Titre.ttf}





begin{document}

fancypage{}{%

    setlength{fboxrule}{2pt}%

    fbox}

vspace{0.3cm}

%vspace{0.2cm}





begin{enumerate}

item



begin{align*}

y(t)&=2(A cosomega_ot-3(Acosomega_ot)^3= 2Acos omega_ot-3A^3cos^3omega_ot\

&=2Acos omega_ot-3A^3(frac{3}{4}cos omega_ot+frac{1}{4}cos3omega_ot)\

&=2Acosomega_ot-frac{9}{4}A^3cosomega_ot-frac{3}{4}A^3cos3omega_ot\

&= left(2A-frac{9}{4}A^3right)cosomega_ot-frac{3}{4}A^3cos3omega_ot\

Second-Harmonic &Distortion= 0%\

Third-Harmonic &Distortion=left|frac{2A-dfrac{9A^3}{4}}{dfrac{3A^3}{4}}right|=

begin{cases}

300%, & text{if} A=1 \

42%, & text{if} A=2

end{cases}

end{align*}

item

begin{tabular}{ c | c}

parbox{0.5textwidth}{

begin{align*}

P_{in}&=500 mW=10 log 500=27 dBm\

P_{out}&=50 mW=10 log 50= 17 dBm\

P_{g_{in}}&=20 mu W=10 log (0/02)= -17 dBm\

L_T&= alpha l= 2X500 Km= 1000 dB

end{align*}

}

&

 parbox{0.5textwidth}{

    begin{align*}

    P_{out}&=P_{out}+G_{T}+L_{T}\

    G_{T}&=G_1+G_2\

    L_T&=L_1+L_2+L_3    

    end{align*}

}

end{tabular}



begin{tabular}{ c | c}



parbox{0.5textwidth}{

begin{align*}

&Section B\

&P_{g_{in}}=P_{in}+0-L_1\

&-17=27-L_1 xrightarrow{~} L_1=44\

&l_1=frac{L_1}{alpha}=22 Km\

&Section D\

&l_3=500-(l_1+l_2)=230/5\

Or\

&P_{out}=P_{g_{2out}}+0-L_3\

&P_{g_{2out}}=P_{g_{2in}}+G_1=478 dBm\

&17=478-L_3 xrightarrow{~} L_1=461 dB\

&l_3=frac{L_3}{alpha}=230/5 Km

end{align*}

}

&

parbox{0.5textwidth}{

begin{align*}

&Section A\

&P_{out}=P_{out}+G_{T}+L_{T}\

&17=27-1000+G_T\

&G_T=990 xrightarrow{so} G_1=G_2=495\

&Section C\

&P_{g_{2in}}=P_{g_{1out}}+0-L_2\

&P_{g_{1out}}=P_{g_{2in}}+G_1=478 dBm\

&-17=478-L_2 xrightarrow{~} L_1=495 dB\

&l_2=frac{L_2}{alpha}=247 Km

end{align*}

} 

end{tabular}



item 



begin{tikzpicture}

draw[step=0.5, gray, very thin](-8.99,-5.99) grid (8.99,-1.03);

draw[thick,->] (-8.5,-3.5) -- (-3,-3.5) node[anchor=south west] {t};

draw[thick,->] (-8.5,-6) -- (-8.5,-1) node[anchor=south west] {$x_c(t)_{DSB}$};



draw[thick,->] (-2.5,-3.5) -- (3,-3.5) node[anchor=south west] {t};

draw[thick,->] (-2.5,-6) -- (-2.5,-1) node[anchor=south west] {$x_c(t)_{AM_{mu=0/5}}$};



draw[thick,->] (3.5,-3.5) -- (8.5,-3.5) node[anchor=south west] {t};

draw[thick,->] (3.5,-6) -- (3.5,-1) node[anchor=south west] {$x_c(t)_{AM_{mu=1}}$};



end{tikzpicture}



item 





begin{tikzpicture}

draw[dotted] (0,0) node[anchor=south west]{DSB} -- (0,5)  ;

path (-8,0) node[anchor=south east]{AM} -- (-8,5) ;

end{tikzpicture}





item 

سیگنال $x(t)$ در شکل زیر نشان داده شده است. از این سیگنال یکبار برای مدولاسیون فرکانس حامل و بار دیگر برای مدولاسیون فاز همان حامل استفاده شده است. 

begin{figure}[h]

    begin{tabular}{*{2}{>{centeringarraybackslash}b{dimexpr0.5linewidth-2tabcolseprelax}}}

        captionof*{×}{}

        الف) رابطه بین $f_Delta$  و $ phi_Delta $  را طوری تعیین کنید که حداکثر فاز سیگنال مدوله شده در هر دو حالت برابر باشد. \

        \

        \

        ب) اگر $f_Delta=phi_Delta=1 $   باشد، حداکثر فرکانس لحظه ایی در هر حالت چقدر است ؟

        &

        begin{tikzpicture}

        draw[thick,->] (0,0) -- (4.5,0) node[anchor=north west] {$t$};

        draw[thick,->] (0,-2) -- (0,2) node[anchor=south east] {$x(t)$};



        coordinate (a) at (1,1);

        coordinate (b) at (2,1);

        coordinate (c) at (2, -1);

        coordinate (d) at (3, -1);

        coordinate (e) at (3,0);



        draw[thick] (0,0) -- (a);

        draw[thick] (a) -- (b);

        draw[thick] (b)-- (c);

        draw[thick] (c) --(d);

        draw[thick] (d) -- (e);

        draw[dotted] (a) -- (1,0);

        draw[dotted] (0,-1)--(2,-1);

        draw[dotted] (0, 1) -- (1,1);



        foreach x in {0,1,2,3,4}

        draw (x cm,1pt) -- (x cm,-1pt) node[anchor=north] {$x$};

        foreach y in {-1,0,1}

        draw (1pt,y cm) -- (-1pt,y cm) node[anchor=east] {$y$}; 

        end{tikzpicture}   

        %caption*{Weighted, complete graph $K_H$}

    end{tabular}

end{figure}







end{enumerate}



 begin{center}

titr  

end{center}

end{document} 

let mi explain my comment. after repairing your code (as far as i guess what you like to obtain), replace tabular environments with tabularx, remove use of parbox (which is probably cause of your problems: for width you should use linewidth and not textwidth), correct tizpicture size (it was to large), use siunitx for units i obtain the following result etc, i obtan the following result:

(gray lines indicate page layout)

mwe:

documentclass[12pt,a4paper]{article}

%usepackage{comment}

%usepackage{setspace}

%doublespacing

%usepackage{amsthm,amssymb,amsmath}

%usepackage{marvosym}

%usepackage{MnSymbol,wasysym,boldline}

%usepackage{roundbox,graphicx,framed}

%usepackage{fontspec}

%usepackage{fancybox}

usepackage[top=10mm, bottom=30mm,

            hmargin=15mm,

            nohead,

            showframe]{geometry}

usepackage{array, tabularx}

usepackage[font=footnotesize, labelfont=bf]{caption}

usepackage{lipsum}

%usepackage{xifthen}

%usepackage{tikz}

usepackage{pgfplots}

usetikzlibrary{arrows,shapes.gates.logic.US,shapes.gates.logic.IEC,calc,shapes,snakes,automata,shapes.geometric}

%usepackage{xepersian}

%DeclareMathSizes{14}{10}{9}{7}

%settextfont[Scale=1]{XB Niloofar.ttf}

%settextfont[Scale=1.1]{B_Nazanin.TTF}

%setdigitfont[Scale=1]{Yas.TTF}

%defpersianfonttitr[Scale=1]{XB Titre.ttf}

usepackage{amsmath}    % missed

newcolumntype{C}{>{centeringarraybackslash}X}

usepackage{siunitx}    % new



begin{document}

%fancypage{}{%

%    setlength{fboxrule}{2pt}%

%    fbox}

%vspace{0.3cm}

%vspace{0.2cm}





begin{enumerate}

item



begin{align*}

y(t)    &=2(A cosomega_ot-3(Acosomega_ot)^3= 2Acos omega_ot-3A^3cos^3omega_ot\

        &=2Acos omega_ot-3A^3(frac{3}{4}cos omega_ot+frac{1}{4}cos3omega_ot)\

        &=2Acosomega_ot-frac{9}{4}A^3cosomega_ot-frac{3}{4}A^3cos3omega_ot\

        &= left(2A-frac{9}{4}A^3right)cosomega_ot-frac{3}{4}A^3cos3omega_ot

text{Second-Harmonic}

        & text{Distortion} = SI{0}{%}    \

text{Third-Harmonic}

        & Distortion = left|frac{2A-dfrac{9A^3}{4}}{dfrac{3A^3}{4}}right| =

    begin{cases}

SI{300}{%}, & text{if} A=1 \

 SI{42}{%}, & text{if} A=2

    end{cases}

end{align*}



item   SI{500}{watt}



begin{tabularx}{linewidth}{ C | C }

$begin{aligned}

P_{in}      & = SI{500}{milliwatt}=10 log 500=SI{27}{dBm}\

P_{out}     & = SI{50}{milliwatt} =10 log 50= SI{17}{dBm}\

P_{g_{in}}  & = SI{20}{microwatt} =10 log (0/02)= SI{-17}{dBm}\

L_T         & = alpha l = 2timesSI{500}{kilometre}= SI{1000}{dB}

end{aligned}$

&

$begin{aligned}

    P_{out}&=P_{out}+G_{T}+L_{T}\

    G_{T}&=G_1+G_2\

    L_T&=L_1+L_2+L_3

    end{aligned}$

end{tabularx}



begin{tabularx}{linewidth}{ C | C }

$begin{aligned}

    &   text{Section B}    \

    &   P_{g_{in}}=P_{in}+0-L_1\

    &   -17=27-L_1 xrightarrow{~} L_1=44\

    &   l_1=frac{L_1}{alpha}=SI{22}{kilometre}\

    &   text{Section D}    \

    &   l_3=500-(l_1+l_2)=230/5\

text{Or}   &   \

    &   P_{out}=P_{g_{2out}}+0-L_3\

    &   P_{g_{2out}}=P_{g_{2in}}+G_1= SI{478}{dBm}\

    &   17=478-L_3 xrightarrow{~} L_1=SI{461}{dB}\

    &   l_3=frac{L_3}{alpha}=SI{230/5}{kilometre}

end{aligned}$

&   $begin{aligned}

    & text{Section A}  \

    & P_{out}=P_{out}+G_{T}+L_{T}\

    & 17=27-1000+G_T\

    & G_T=990 xrightarrow{so} G_1=G_2=495\

    & text{Section C}\

    & P_{g_{2in}}=P_{g_{1out}}+0-L_2\

    & P_{g_{1out}}=P_{g_{2in}}+G_1= SI{478}{dB}\

    & -17=478-L_2 xrightarrow{~} L_1= SI{495}{dB}\

    & l_2=frac{L_2}{alpha}= SI{247}{kilometre}

    end{aligned}$

end{tabularx}



item



begin{tikzpicture}

draw[step=0.5, gray, very thin] (-7.99,-5.99) grid (8.49,-1.03);

draw[thick,->] (-7.5,-3.5) -- (-3.0,-3.5) node[anchor=south west] {t};

draw[thick,->] (-7.5,-6)   -- (-7.5,-1)   node[anchor=south west] {$x_c(t)_{DSB}$};



draw[thick,->] (-2.5,-3.5) -- (3,-3.5)  node[anchor=south west] {t};

draw[thick,->] (-2.5,-6.0) -- (-2.5,-1) node[anchor=south west] {$x_c(t)_{AM_{mu=0/5}}$};



draw[thick,->] (3.5,-3.5) -- (8.5,-3.5) node[anchor=south west] {t};

draw[thick,->] (3.5,-6.0) -- (3.5,-1)   node[anchor=south west] {$x_c(t)_{AM_{mu=1}}$};

end{tikzpicture}



item



begin{tikzpicture}

draw[dotted] ( 0,0) node[anchor=south west]{DSB} -- (0,5)  ;

draw[dotted] (-8,0) node[anchor=south west]{AM}  -- (-8,5) ;

end{tikzpicture}





item $x(t)$

%سیگنال $x(t)$ در شکل زیر نشان داده شده است. از این سیگنال یکبار برای مدولاسیون فرکانس حامل و بار دیگر برای مدولاسیون فاز همان حامل استفاده شده است.

begin{figure}[htb]

    begin{tabular}{*{2}{>{centeringarraybackslash}b{dimexpr0.5linewidth-2tabcolseprelax}}}

    caption{?}% not clear

 %        الف) رابطه بین $f_Delta$  و $ phi_Delta $  را طوری تعیین کنید که حداکثر فاز سیگنال مدوله شده در هر دو حالت برابر باشد. \

%        \

%        \

%        ب) اگر $f_Delta=phi_Delta=1 $   باشد، حداکثر فرکانس لحظه ایی در هر حالت چقدر است ؟

        &

        begin{tikzpicture}

        draw[thick,->] (0,0) -- (4.5,0) node[anchor=north west] {$t$};

        draw[thick,->] (0,-2) -- (0,2) node[anchor=south east] {$x(t)$};



        coordinate (a) at (1,1);

        coordinate (b) at (2,1);

        coordinate (c) at (2, -1);

        coordinate (d) at (3, -1);

        coordinate (e) at (3,0);



        draw[thick] (0,0) -- (a);

        draw[thick] (a) -- (b);

        draw[thick] (b)-- (c);

        draw[thick] (c) --(d);

        draw[thick] (d) -- (e);

        draw[dotted] (a) -- (1,0);

        draw[dotted] (0,-1)--(2,-1);

        draw[dotted] (0, 1) -- (1,1);



        foreach x in {0,1,2,3,4}

        draw (x cm,1pt) -- (x cm,-1pt) node[anchor=north] {$x$};

        foreach y in {-1,0,1}

        draw (1pt,y cm) -- (-1pt,y cm) node[anchor=east] {$y$};

        end{tikzpicture}

        caption*{Weighted, complete graph $K_H$}

    end{tabular}

end{figure}



end{enumerate}



% begin{center}

%titr

%end{center}

end{document}

please check, if the introduced changes can help you. at least on this code try to write new mwe, which we will able to test and further help you.

off-topic: to my taste the structure of your document is not clear. you should reconsider it.