Trig Help...?????????????

This is what I hate. You get a math problem saying cos(43)=?. You type in cos on your calculator and then you press 34 and hit the equals on, but the multiple choice answer always has different angles (yes, they are in degrees, not radians). Sometimes you get a negative value and you have to do an extra step which is to subtract it from 180 or something. Please show how to find all the possible values for cos, sin, and tan. I'm pretty sure this isn't the same thing as periods because you end up at that same place in the quadrant. It has something to do with subtracting from 180 or 90, I just don't understand that concept.