Question

【高数级数问题】题目如图，求解具体解题过程！！

Answer 1

an>0, bn>0, ∑<n=1,∞> bn 收敛， 则 ∑<n=1,∞> sin(bn/2) 收敛.
cosan-an=cosbn,
得 an = cosan-cosbn ≤ 1-cosbn = 2[sin(bn/2)]^2
an/bn<an/|2sin(bn/2)| ≤ |sin(bn/2)|
则 ∑<n=1,∞>an/bn/ 收敛,