I feel bad about asking you for help all the time but i have no one else to turn to (except for a professor who sucks) and i have spent my day trying to solve this and several other trig-problems.

I am to find when some of these alternatives below cos x+ sin x=0 I have already tried with a calculator and it almost always comes out wrong and it takes ages to try all the options, the profossor doesn't explain anything and expects me to know this trigonometry crap without any previous experience.

Help is as always very much appreciated!