Clear[x, y, t,a, b,  tmini,tmaxi]
a=5;
b=2;
tmini = -10*Pi;
tmaxi=10*Pi;
{x[t_],y[t_]}={(a-b)*Cos[t]+b*Cos[(a-b)/b*t],(a-b)*Sin[t]-b*Sin[(a-b)/b*t]};

hypocycloid=
	ParametricPlot[{x[t],y[t]},{t,tmini,tmaxi},
	PlotStyle->{{Blue,Thickness[0.015]}},
	AspectRatio->Automatic,AxesLabel->{"x","y"}]