Stavros Macrakis wrote: [snip] > For your last case, try rootscontract. .... Thanks. But sorry that I had erred in what I reported. Now rootscontract(radcan(sqrt(1-y^6)/sqrt(1-y^2))); gives -sqrt(y^4+y^2+1). I expect however sqrt(y^4+y^2+1). M. K. Shen