Please tell me how to solve them, thank you!

2. (a) (5 points) Determine the convergence or divergence of the series n sin ((2n + 1)27/3) n>1 Hint: A certain one of the series tests from the book/lecture notes may be very helpful here. (b) (5 points) Prove that if f : R - R is a bounded, real-valued function with lim, to f () = 0, then the series Elf (1) . f (2 ) . .. f(n)) n>1 converges. (That is, the nt term of this series is f (1) times f(2) times . .. times f (n))