Sin and Cos can take decimals as well, which means you'll need far more than 360 items, unless you don't care about accuracy. The initial post used decimal angles, so presumably more accuracy is required for that poster.
Doesn't usually matter... 360 is more distinct degrees than you'll ever need for most stuff and the really important factor is that you can have decimals returned so using parametric equations (and the like) to plot movement remains pretty convincing. If you REALLY want to optimise, you work in ints on a large scale then factor them down for rendering anyway... something else that isn't really worth the bother on a modern PC.
2. We only need to Dim the arrays of 360 elements because that is all people use.
No, it's not. Employing two tables is overkill; instead dim a single array of 450 elements, write the sin of each element to it and you have sin(x) as table(x) AND cos(x) as table(x+90). Much smaller table, same functionality.