非应届生,防雷
单选 (3) / (5) / (4)
多选 (3)(5) / (1)(4) / (2)(5) / (1)(4) / (2)(4)
选填 9,-2 / 2,6,-3 / 15
非选 1. (1)π/72 (2)60度 (3)6:22
2. (1)略 (2)-1/8 (3) (1/5)^(2n+1) + (1/5)^(2n+2) - (1/3)^(2n+1)
= (1/5)^(2n+1) * (6/5) - (1/3)^(2n+1)
= (1/5)^(2n) * (6/25) - (1/3)^(2n) * (1/3) < 0
(1/5 < 1/3 且 6/25 < 1/3)
利用递减数列跟 0、-1/8分别是上下界可说明不等式恒成立