Additional conditions for expression

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 ?