The whole circle
I don't know if this looks like what you expect, but here's how you could plot a parametric curve, and fill the region between them. Don't know if the filling is something you want though. Note that the trigonometric functions assume degrees by default, which is why I've used deg(t) in those.

\documentclass[border=4mm]{standalone} \usepackage{pgfplots} \pgfplotsset{width=12cm,compat=1.12} \usepgfplotslibrary{fillbetween} \begin{document} \begin{tikzpicture} \begin{axis}[ title=My title, ylabel = {$y$}, xlabel = {$x$}, ] \addplot[ domain=0:2*pi, samples=100, variable=t, name path=A ] ( {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*cos(deg(t))}, {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*sin(deg(t))} ); \addplot[ thick, domain=2*pi:4*pi, samples=100, variable=t, name path=B ] ( {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*cos(deg(t))}, {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*sin(deg(t))} ); \addplot [blue,opacity=0.1] fill between[of=A and B]; \end{axis} \end{tikzpicture} \end{document}
Show just some quadrants
If you want to show just parts of this, you could of course adjust the domain. Perhaps easier is to just set xmin, xmax, ymin and ymax to whatever you like. For example:

\documentclass[border=4mm]{standalone} \usepackage{pgfplots} \usepgfplotslibrary{fillbetween} \begin{document} \begin{tikzpicture} \begin{axis}[ width=10cm, height=6cm, title=My title, ylabel = {$y$}, xlabel = {$x$}, xmin=-1.1,xmax=1.1, ymin=-1.01,ymax=0, ] \addplot[ red, thick, domain=0:2*pi, samples=100, variable=t, ] ( {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*cos(deg(t))}, {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*sin(deg(t))} ); \addplot[ blue, thick, domain=2*pi:4*pi, samples=100, variable=t, ] ( {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*cos(deg(t))}, {(1/2)*(exp(exp(-t))+exp(exp(-t-2*pi)))*sin(deg(t))} ); \end{axis} \end{tikzpicture} \end{document}
Completely different route
If you want to demonstrate that it becomes a circle, perhaps you could plot the distance from the origin as a function of t instead:

\documentclass[border=4mm]{standalone} \usepackage{pgfplots} \begin{document} \begin{tikzpicture} \begin{axis}[ title=Distance from origin, ylabel = {$r$}, xlabel = {$t$}, xticklabel={$\pgfmathprintnumber{\tick}\pi$}, ] \addplot[ red, thick, domain=0:6*pi, samples=100, ] (x/pi,{sqrt(((1/2)*(exp(exp(-x))+exp(exp(-x-2*pi)))*cos(deg(x)))^2 +((1/2)*(exp(exp(-x))+exp(exp(-x-2*pi)))*sin(deg(x)))^2)}); \end{axis} \end{tikzpicture} \end{document}
pgfplotsandpstricks. For first one is worth to look in example galleryhttp://pgfplots.net/and of course read manual for this packages. ON this basis try to construct "Minimal Working Example (MWE)". Otherwise, this question will treat asdo-it-for-me..*in the equations. It couldn't be the same as*