Frequency domain - mechanical

Hi,
I am an electronics student and am trying to simulate the mechanics of a square plate.
My plate has the 4 side faces fixed and a uniform distributed load on one of the larger faces.
The stress and displacement are close to calculated values - hence I can justify that my understanding is verified by the simulation.
I tried to find the eigen frequencies. My query - is the solution given by comsol for eigen frequency = omega (= 2.pi.f) or is it = "f"?
I tried the frequency domain simulation. Here, the frequency that I enter are omega (= 2.pi.f) or is it "f"?

Please recommend me books where, from formulae, I can calculate the resonant frequency and compare with the simulated results. I tried Timoshenko - strength of materials -2, but did not get the frequency.

Thanks in advance.