We will choose for comparison the p-series ∑n=1∞ 1/n2 which is convergent since p = 2 and 2 > 1.
0 ≤ sin2n ≤ 1 for all n ∈ Ν , and n2 + 5 > n2 for all n ∈ N.
So, since each term in the given series is smaller than the corresponding term in the p-series, the series converges.