# How to draw a cone trunk planning?

I want to illustrate the calculation of lateral area cone trunk. I can do the first and the third drawing but I can't do the second. \documentclass{article}

\usepackage{tikz}

\begin{document}

\begin{center}

\begin{tikzpicture}

\draw (-1,0) arc (180:360:1cm and 0.5cm);

\draw (-1,0) arc (180:0:1cm and 0.5cm);

\draw (-2,-3) arc (180:370:2cm and 1cm);

\draw[dashed] (-2,-3) arc (180:10:2cm and 1cm);

\draw(-2,-2.9)  -- (-1,0);

\draw(2,-2.9)   -- (1,0);

\draw [dashed](-2,-2.9)  -- (2,-2.9);

\draw[dashed](0,-2.9) --(0,0);

\draw[dashed](-0.6,0.4,) --(1,0);

\node at (0.3,-1.4) {\textbf{h}};

\node at (0,-3.2) {\textbf{R}};

\node at (0,0.2) {\textbf{r}};

\shade[left color=blue!5!white,right color=blue!60!white,opacity=0.3] (-1,0) arc (180:360:1cm and 0.5cm) -- (2,-3) arc (360:180:2cm and 1cm) -- cycle;

\shade[left color=blue!5!white,right color=blue!60!white,opacity=0.3] (0,0) circle (1cm and 0.5cm);

\end{tikzpicture}

\end{center}

\end{document}


You may add something like the following (using polar coordinates to specify the points) inside your tikzpicture:
\begin{scope}[xshift=5cm,yshift=1cm]
\node at (-90:1.5cm) {$2\pi r$};
\node at (-90:4.5cm) {$2\pi R$};