√n² <√(n²+1) <√[n²+1+1/(4n²)]即 n <√(n²+1) < n + 1/(2n) lim(n→∞)sin(nπ)= 0 lim(n→∞)sin{[n+1/(2n)]π} = lim(n→∞) [sin(nπ)cos(π/2n)+ cos(nπ)sin(π/2n)] = 0∴lim(n→∞)sin{[√(n²+1)]*π} = 0