Plot the change in potential energies depending on the angle phi

Questions
,
1

I have a task where I need to display in the graph the change in potential energies depending on the angle phi, but I need to change phi and get the values of potential energies. And get stable segments of the mechanism on the chart

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2

This is an attempt:

func[phi_] = Sin[2*phi] - 0.5;
Manipulate[
 Plot[func[phi], {phi, -Pi, Pi}, 
  Epilog -> {Line[{{\[Phi], 0}, {\[Phi], func[\[Phi]]}, {0, 
       func[\[Phi]]}}]}],
 {\[Phi], -Pi, Pi, Animator}]