Keep in mind that cosine is negative in the second and third quadrants.

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.

--Chris