cosY= -sqrt3/2 for y in [pi,2pi]
The question ask to solve these equations
The second question is asking for particular angles within the interval . Note that you will only have one solution.
keep in mind that Change the angle to get
The first question wants you to generalize the solution. This can be a little tricky. Find several solutions to the equation, and then try to find a pattern given in the coefficients of the angles. Try this one and let us know where you get stuck...if you get stuck...
I hope this helps.