It was a simple case of rushing through the problems. I also think that posting questions from all categories per set is not a good idea. You see, I can answer most of the trig questions on my own. To do a systematic study will take us 100 years to finish Cohen's thick book of questions. I am going to go through most of the questions at the back of each set and post ONLY THE PROBLEMS I GET WRONG OR DO NOT UNDERSTAND OR SOME CHALLENGING PROBLEMS FROM THAT CATEGORY.