Hi (sorry for bad eng.), i have next code
reset()
var('K1, T1, T2')
var('p')
# Transient function W(p)
W = K1 * p / ((T1 * p - 1) * (T2 * p - 1))
# Amplitude-phase-frequency characteristic W(jw)
Wa(omega) = W(p = I * omega)
Re(omega) = Wa(omega).real()
Im(omega) = Wa(omega).imag()
print(Re)
but last string gives loooooong result, because sagemath don't knows that K1, T1, T2 and omega are real, how to "tell" that to sagemath