(2), the original formula =1/2 * (1/3+1/3-1/5+1/7+65438. ( 1- 1/ 1 1)= 1/2* 10/ 1 1=5/ 1 1;

The original formula =1/2 * [1-kloc-0//3+1/3-1/5+1/7+-+65438. (2n+ 1)]= 1/2 * 2n/(2n+ 1)= n/(2n+ 1)；

(3), the original formula = n/(2n+1);

(4), the original formula =1/(x-1)-1/x+1(x+1)+1(x-/kloc-0)