Must the angle from the ground to the inclined plane be given to you as part of the question ?

Not necessarily. It depends what the question is asking. For example, if a 2000 kg car is coasting along a flat surface at 40 km/h, then it drives up a hill (a.k.a. an inclined plane), how high up the hill will it travel (ignoring friction)?

The answer to that question is independent of the angle of the hill. It's just a matter of converting the car's kinetic energy before the climb to potential energy once it comes to rest.

Do you have a particular question that's stumping you? If you're stuck, one of us here may be able to provide some guidance.