3 S3=S,+arctan arctan+arctanarctan 18 3 18 k-1 偎设S1= arctan k-1 k arctan +arctan arctan 2 2K k+1 Sn= arctan→ arctan=,(n→>) n+1 故∑ arctan 上一页下一页返回18 1 arctan 3 2 = arctan + 18 1 s3 = s2 + arctan , 4 3 = arctan arctan1 1 arctan → +  = n n sn ( ) 4 = n →   2 2 1 arctan 1 arctan k k k sk + − = , 1 arctan + = k k , 1 1 arctan k k sk − 假设 − = . 2 4 1 arctan 1 2   =  n= n 故