ok

unrad(root(cosh(x),3)/x*root(x+1,5)-1)
unrad(S('(x+y)**(2*y/3) + (x+y)**(1/3) + 1')) == (s**(6*y) + s**3 + 3*s**2 + 3*s + 1, [(s, s**3 - x - y)])  should it fail -- change _take
unrad(sqrt(cosh(x)/x)+root(x+1,3)*sqrt(x)-1)