Change the length of the pendulum to achieve the analysis of the pendulum frequency change, but I scan the frequency of the two images do not correspond to each other, what is the problem?

sweep.mw

I analyzed the kinetic equation of the system and got this formula. I want to realize the sweep frequency analysis of the kinetic function by changing the size of omega2, but I don't know how to write a program. Want to ask for help

solve831.mw

Singular points appear in the solution and rendering of this program. If the data does not converge when taking a short time step, what should I do if I want to cross the singular point and continue drawing the image?solve826.mw

I want to solve for the intrinsic frequency of a structure by using the equation of the determinant of a matrix equal to 0. I don't know if this is the correct procedure. Also the result is too complicated, what does z mean? Is it possible to simplify the result?