The sixth question, because for any M>0 Xo always belongs to (m, +∞), makes COSXo= 1, thus Y = XOCOSXO = 0.

The seventh problem is proved to be unbounded on the interval (0, 1).

Because for any M>0, the point Xo can always be found in (0, 1), so that f (XO) >; M. for example, if Xo=(k belongs to n), then f(Xo)=2kπ+, and when k is large enough, f (XO) >; M, so it is unbounded on (0, 1.

Prove again that it is not infinite.

Because Xo can always be found for any M>0, n>0, so 0