Plotting parametric curves

If we want to plot the parametric curve x(t), y(t), tmin≤t≤tmax...

x = Cos[t];
y = Sin[t];
tmin = 0;
tmax = 2 Pi;

then we can use the following Mathematica command:

ParametricPlot[{x, y}, {t, tmin, tmax}, 
      AspectRatio -> Automatic]