Is the function y = xcosx bounded in (- ∞, + ∞)? Is it infinite when x → + ∞? Why Because when a, M > 0 and x > 0 are written back, there will always be x0 ∈ (x, + ∞), so that cosx0 = 0 and y = x0cosx0 = 0

Is the function y = xcosx bounded in (- ∞, + ∞)? Is it infinite when x → + ∞? Why Because when a, M > 0 and x > 0 are written back, there will always be x0 ∈ (x, + ∞), so that cosx0 = 0 and y = x0cosx0 = 0

When x → + ∞, f (x) is infinite. The definition is: for any large positive number m, there is a positive number x, for any x > x, there is always | f (x) | > M. analysis: when x is large, there is always X that makes cosx = 0, so | f (x) | > m can not be constant