I quite frequently see clock-related behaviors, and in fact they are the most noticeable as they are periodic and you just need to watch for an action occurring over and over again. There are two simply for variety.
As for the diagram, I think it is accurate. When you take the absolute value of a number, you get the number back, but if it was negative, it is made positive. So, when the sine function returns a negative number as normal, the absolute value of it simply makes it positive instead. So any "wave troughs" become "wave crests." Normal "wave crests" remain the same, effectively making the resulting graph. If you have a graphing calculator or
This beautiful tool, you can check it for yourself.