Leave it in radians and in terms of . With these questions always leave it in the units which the question is given in. For all but the most basic trig you'll be using radians anyway

As you can gather from the graph is symmetrical in the line

This means that the distance between and is equal to the distance between and

Hence which should be (which is roughly 157.5 degrees)

For part b use the same principle to get which is a perfectly acceptable answer and again the same answer you got