Reply by October 27, 20082008-10-27
If X(w) is the Fourier Transform (FT) of x(t), I know that the FT of dx(t)/dt is jwX(w). Using the duality property I obtained that the FT of tx(t) is (2pi/j)(dX(-w)/dw), but I found in a table that the correct FT is in fact jX(w). Could you help me to find the mistake here?

I will be thankful if somebody could help me with that.
Luis Felipe