documentclass[11pt]{articl}

usepackage{color}

usepackage{tikz}

%usepackage[latin1]{inputenc}

usepackage{pgfplots}

pgfplotsset{compat=1.11}

begin{document}

begin{center}

begin{tikzpicture}

begin{axis}[

width=linewidth,

trig format plots=rad,

axis lines = middle,

xlabel={$theta=wt$},

xlabel style={at={(1,0.5)},anchor=west},

enlargelimits,

ytick={empty},

extra y ticks={1,0.5,0,-0.5,-1},

extra y tick labels={$V_m$,$I_m$,0,$-I_m$,$-V_m$},

xtick={-6.28318, -4.7123889, …, 6.28318},

xticklabels={

$-2pi$, $-frac{3pi}{2}$, $-pi$, $frac{pi}{2}$, ,

$frac{pi}{2}$, $pi$, $frac{3pi}{2}$, $2pi$},

clip=false]

addplot[domain=-2*pi:2*pi,samples=200, red] {0.5*sin(x)};

addplot[domain=-2*pi:2*pi,samples=200, blue, dashed] {sin(x-2)};

draw[dotted,blue!40] (axis cs: 0,1.1) — (axis cs: 0,0);

draw[dotted,red!40] (axis cs: 1,1.1) — (axis cs: 1,0);

draw[dashed,olive,<->] (axis cs: 0,1.1) —

node[above,text=black,font=footnotesize]{$phi$} (axis cs: 1,1.1);

coordinate (P) at (axis cs:1.5*pi,{sin(25)});

node (labelV) at (axis cs:2*pi,{1+sin(2*pi)}) {Voltage $(V)$};

draw [red!50!black, thick, dashed, ->, shorten >=2pt] (labelV) — (P);

coordinate (Q) at (axis cs:-1.5*pi,{sin(30)});

node (labelI) at (axis cs:-2*pi,{1+sin(2*pi)}) {Current $(I)$};

draw [red!50!black, thick, dashed, ->, shorten >=2pt] (labelI) — (Q);

end{axis}

end{tikzpicture}

end{center}

end{document}