ketz said:
why it's impossible for a satellite in a non-equatorial plane to be geostationary? Explain in terms of gravitational force and centripetal force(If possible show equations and draw diagrams for forces acting on the satellite).
The two extremes if one can call them that, is a satellite orbiting on the equatorial plane and one orbiting on the polar plane ( is crossing the north and south pole). And in between are any other number of circullar orbits at an angle to the equatorial plane.
Obviously a polar orbit cannot be geostationary.
Not all equatorial plane orbits are geostionary - that would depend upon the altitude of the satellite. ( which by the way is what your question is presumably asking about, but I am not so sure).
By your diagram, or is that the diagram supplied by the question, the orbit displayed is parallel to the equator and that just cannot happen unless of course the satellite expends fuel and supplies a thrust to conteract the resultant force arising from gravitation and keep it at that plane.
The question appears not explicite enough to provide a complete and concise answer.
Depending upon the analysis, a satellite not in a non-equatorial plane but parallel to, can be geostationary so the answer would be Yes it can, and you would not be incorrect.