I was working on practice test 0177, problem 51. It is easy to solve using Malus's law. However, one step in the solution requires knowing the cosine of 45 degrees. This is easy enough with a calculator, but calculators aren't allowed on the exam (unless I am SERIOUSLY misinformed). So what do I have to do? Do I have to spend time memorizing the signs and cosines of different values so I can get questions like problem 51 correct on the exam?

While we are on the subject, another problem on test 0177 (I forget which problem) required a knowledge of the value of ln 4, or something like that. In my Physics courses, whenever I had to solve something like that I would use a calculator, which, again, isn't allowed on the exam. I can't solve it without a calculator. So what should I do? Do I have to spend time memorizing the values of different ln values for the Physics GRE? What else about math should I teach myself (or memorize)? Is there a better way to go about solving problems like 51 other than memorizing the values of different cosines? Thanks.