高考数学考点专题总复习5
1.已知集合A ={x | x =cos 3k π, k ∈Z },B ={x | x =sin π-6
3k 2, k ∈Z },则有
(A )A ?B (B )A ?B (C )A ≠B (D )A =B
2.当x ≠21k π(k ∈Z )时,ctgx x cos tgx x sin ++的值
(A )恒为非负值 (B )恒为正值 (C )恒为负值 (D )恒为非正值
3.将函数y =sin3x 的图象作下列哪种平移,可得函数y =sin(3x +6π)的图象
(A )向左平移6π (B )向左平移18π (C )向右平移6
π (D )向右平移18
π 4.函数y =|sin x |+sin|x |的最小值是
(A )-1 (B )0 (C )1 (D )以上答案都不正确
5.已知f (sin x -1)=cos 2x +2,则f (x )的表达式是
(A )f (x )=-x 2-2x +2, x ∈[0, 2] (B )f (x )=-x 2-2x +2, x ∈[-2, 0]
(C )f (x )=x 2+x -2, x ∈[-2, 0] (D )f (x )=x 2+x -2, x ∈[0, 2]
6.已知5sin θ+12cos θ=0,则θ
-θ+θsin 32cos 9sin = . 7.函数y =x sin 1log 21
++x sin 1log 21-的递减区间是
8.设定值a ∈(0, 1),试求函数y =
1
a x cos a 2)a x (cos a 2+++的最值。
参考答案
D
B B B B 62331033或- Z k ],k 2,2
k 2(]k 2,2k 2(∈ππ-ππ+ππ+π和 8.解:∵ y =
1a x cos a 2)a x (cos a 2+++, ∴ 2ay cos x +a 2y +y =a cos x +a 2, ∴ cos x =)1y 2(a y y a a 22---, 故
-1≤)1y 2(a y y a a 22---≤1, 当2y -1>0时, 解得y ≥
1a a +且y ≤1a a -, 无解(∵ 0 a a -≤y ≤1a a +, ∴ 当cos x =1时y 的最大值是y max = 1a a +, 当cos x =-1时, y 的最 小值是y min = 1a a -.