foo=DedekindEta[12 I] -> ((-1 + Sqrt[2])^(3/4) (-1 + Sqrt[3])^(1/6) Gamma[1/4])/( 2^(25/48) 3^(3/8) (2 + 3^(1/4) + Sqrt[3] (Sqrt[2] + 3^(1/4))) \[Pi]^(3/4)); Macsyma had a function named INPART almost identical to Mathematica's Part. Almost nobody used it, for the same reason that Part is a pain in the tush. Everybody used Macsyma's PART, which I really miss. I now realize it was brilliant: Part 1 of a quotient is the numerator, part 2 is the denominator. Clear@ndpart ndpart[xp_, 1, L___] := ndpart[Numerator@xp, L] /; Denominator@xp =!= 1 ndpart[xp_, 2, L___] := ndpart[Denominator@xp, L] /; Denominator@xp =!= 1 ndpart[xp_, p_, L___] := ndpart[xp[[p]], L] ndpart[xp_] := xp So the third factor of the denominator of the right side of foo is In[633]:= ndpart[foo, 2, 2, 3] Out[633]= 2 + 3^(1/4) + Sqrt[3] (Sqrt[2] + 3^(1/4)) In[634]:= Position[foo, %] Out[634]= {{2, 5, 1}} Was that your guess? —Bill