def r(h): return r5*h^(3/2)
def Px(h,t): return r(h)*cos(t)
def Py(h,t): return r(h)*sin(t)
def Pz(h, t): return H*h
pent = parametric_plot3d((Px, Py, Pz), 
           (0,1), (0, tau),
           plot_points=[40,6])
pent.show()