ï¼1ï¼å 为an+an+2n=â«1nÏ40tannx(1+tan2x)dx=â«1nÏ40tannxsec2xdx令tanx=tï¼åï¼ä¸å¼=1nâ«10tndt=1n(n+1)åé¨ååæ°åSnï¼niï¼11i(ai+ai+2)=niï¼11i(i+1)=1?1n+1ælimnââSnï¼1å æ¤ânï¼11n(an+an+2)ï¼1ï¼2ï¼è¯æï¼å
估计ançå¼ï¼å 为anï¼â«Ï40tannxdxã
温馨提示:答案为网友推荐,仅供参考