sine/cosine function -----> are both true for when it is negative?

Do the following rules properly describe at which intervals both the unrestricted sine and cosine functions are negative? Is only one of them right or both?

1) [Xmin - period/4, Xmin + period/4]

2) [x2 + pn, x1 +pn] (p = period) (n = integers)

I'm trying to find similar points using my calculator with these two rules and I can't seem to find any which leads me to believe, I am doing something wrong or these rules are wrong.

Please help!