Drawing some stuff on Tikz

Question

Can you guys help me doing those things like the one that is signed/encircled in the picture below?

\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
    [scale=30,line cap=round,line join=round,x=0.06cm,y=0.03cm]
%\draw[mygreen!20, fill = mygreen!20] (0,0.5)--(0,1.375)--(4.2,0.325)--(4.0,-0.5)--(2,0)--cycle; 
\draw[very thick, ->, >=stealth] (-0,0) -- (4.5,0) node[anchor=north] {Tempo};
\draw[very thick,->, >=stealth] (0,0) -- (0,4.5) node[anchor=east] {Nível de Inventário};

\draw[very thick, domain=0:1.5, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+3)});  
\draw [very thick, black!70, samples=200, dashed] (1.5,-3/2) -- (1.5,3);
\draw[very thick, domain=1.5:3, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+7.5)});
\draw [very thick, black!70, samples=200, dashed] (3,-3/2) -- (3,3);    
\end{tikzpicture}
\end{document}

Answer 1

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
        [scale=30,line cap=round,line join=round,x=0.06cm,y=0.03cm]
        %\draw[mygreen!20, fill = mygreen!20] (0,0.5)--(0,1.375)--(4.2,0.325)--(4.0,-0.5)--(2,0)--cycle; 
        \draw[very thick, ->, >=stealth] (-0,0) -- (4.5,0) node[anchor=north] {Tempo};
        \draw[very thick,->, >=stealth] (0,0) -- (0,4.5) node[anchor=east] {Nível de Inventário};

        \draw[very thick, domain=0:1.5, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+3)});  
        \draw [very thick, black!70, samples=200, dashed] (1.5,-3/2) -- (1.5,3);
        \draw[very thick, domain=1.5:3, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+7.5)});
        \draw [very thick, black!70, samples=200, dashed] (3,-3/2) -- (3,3);    
        \draw[fill = black] (0,0) node[anchor=north east, rotate=0] {$0$}; 
        \draw[fill = black] (1.5,0) node[anchor=north east, rotate=0] {$T$};
        \draw[fill = black] (3,0) node[anchor=north east, rotate=0] {$T$};  
        \draw [very thick, |-, black!70, samples=200, dashed] (-0.40,0) -- (-0.40,1.2); 
        \draw [very thick, -|, black!70, samples=200, dashed] (-0.40,1.8) -- (-0.40,3); 
        \draw[fill = black] (-0.40,1.5) node[ rotate=0] {\small$Q-L_E$};
        \draw [very thick, |-, black!70, samples=200, dashed] (1.7,0) -- (1.7,-0.5);
        \draw [very thick, -|, black!70, samples=200, dashed] (1.7,-1) -- (1.7,-3/2);
        \draw[fill = black] (1.7,-0.65) node[rotate=0] {\small$L_E$};
        \end{tikzpicture}
\end{document}