1.函数y=sin(x+π/4)的单调递减区间是?2.函数y=2sin(2x+π/3)取最大值时x的集合?

题目

1.函数y=sin(x+π/4)的单调递减区间是?2.函数y=2sin(2x+π/3)取最大值时x的集合?
第一题是一道选择题( )
[π/2,π] B,[0,π/4] C,[-π,0] D,[π/4,π/2]

答案

1.(1).验A π/2≤x≤π ==>π/2+π/4≤x+π/4≤π+π/4 ==>3π/4≤x+π/4≤5π/4 (T)(2).验D π/4≤x≤π/2==>π/4+π/4≤x+π/4≤π/2+π/4 ==>π/2≤x+π/4≤3π/4 (T)A,D都是对的题目错了2.当2x+π/3=π/2+2kπ ...