Determine whether the series is convergent or divergent by expressing Sn as a telescopic sum (as in example 7). If it is convergent, calculate its sum

Answer:
Convergent
cos 1 − 1
Step-by-step explanation:
∑ (cos 1/n² − cos 1/(n+1)²)
= lim(n→∞) [(cos 1 − cos 1/4) + (cos 1/4 − cos 1/9) + ... + (cos 1/n² − cos 1/(n+1)²)]
= lim(n→∞) [cos 1 − cos 1/(n+1)²]
= cos 1 − cos 0
= cos 1 − 1
The series converges to cos 1 − 1.