May be I am wrong, but I thing that correct result should be True.
Am I making a mistake, or not?
In[2]:= Assuming[ci != 0, (Sign[ci]^2 == 1) // FullSimplify] Out[2]= Sign[ci]^2 == 1
Thanks!
Mathematica thinks with complex numbers and the identity is not true with complex numbers.
Assuming[ci != 0 && Element[ci, Reals], (Sign[ci]^2 == 1) // FullSimplify]
