函数y=sin(−2x+π6)的单调递减区间是( ) A.[−π6+2kπ,π3+2kπ] k∈Z B.[π6+2kπ,5π6+2kπ] k∈Z C.[−π6+kπ,π3+kπ] k∈Z D.[π6+kπ,5π6+kπ] k∈Z
问题描述:
函数y=sin(−2x+
)的单调递减区间是( )π 6
A. [−
+2kπ,π 6
+2kπ]π 3
k∈Z
B. [
+2kπ,π 6
+2kπ]5π 6
k∈Z
C. [−
+kπ,π 6
+kπ]π 3
k∈Z
D. [
+kπ,π 6
+kπ]5π 6
k∈Z
答
∵y=sin(−2x+
)=-sin(2x-π 6
)π 6
令−
+2kπ≤2x−π 2
≤π 6
+2kππ 2
则−
+kπ≤x≤π 6
+kππ 3
∴函数y=sin(−2x+
)的单调递减区间[−π 6
+kπ,π 6
+kπ],k∈Zπ 3
故选C.