Earlier quoted context omitted.
It wouldn't have been a problem if it instead used an index variable i ranging from 0 to the number of sides, computing 2 pi i/sides along the way. If you're going to rely on repeated addition of irrational numbers to come out to some exact value, then you've misunderstood the abilities of finite decimal representations. It is something easy to overlook, but shouldn't be too surprising to someone who has computed any…
I fully agree. As a more general strategy, just use integers (preferably unsigned integers) for all critical stuff such as state handling and looping over. Then, perform floating point operations only on top of that, as a last step. Sometime you don't even need that and use fixed point arithmetics instead (i.e. change your unit to some fixed fraction, e.g. in accounting calculate with integer cents instead of floatin…
Right. "Once you go float, you never go back."
Any time you need discrete operations like counting and equality, do it in integer space. Avoid going from integer space back to floating point space.