e 欲使截断误差n< πn1(2n+1)-22m104 则n应满足√元·nl(2n+1)22m>104→n≥4 取n=4,则所求积分近似值为 erd- 22.324.5.2126.73别 ≈0.5205 ( ) 2 7 3! 1 2 5 2! 1 2 3 1 1 1 2 4 6   −   +   −   e −x dx = 2 2 1 0 2          +   −   +  = −  2 7 3! 1 2 5 2! 1 2 3 1 1 1 2 4 6  n n n n r 2 !(2 1) 2 1 1 +    4 10−  2 4  !(2 +1) 2 10 n 则n应满足  n n e x x d 2 2 1 2 0  −  则所求积分近似值为 欲使截断误差  0.5205