<p>On the exam does cos(pie/4) = 1/(radical 2). I'm used to seeing (radical 2)/2. This is how Cracking the Calculus AB & BC Exam has it.</p>
<p>When you get to the point where you’re doing calc and not just arithmetic, you eventually stop caring about rationalizing denominators and just go with the shortest way to write it.
Try writing 1/sqrt(2) and sqrt(2)/2 ten times each. See which one’s easier. :)</p>
<p>The AP Exam will more likely write sqrt(2)/2 on the actual multiple choice answer choices that you’re looking at, but will accept either in terms of responses on the Free Response. Within the question itself, they could theoretically use either.</p>