cosωx - sinωx = sqrt(2) (cosωx cosπ/4 - sinωx sinπ/4)
= sqrt(2) cos(ωx + π/4)
该函数在 2kπ <= ωx + π/4 <= (2k+1)π 上单调递减
-π/2 < x < π/2
2kπ <= -πω/2 + π/4, ω <= 1/2 - 4k
ωπ/2 + π/4 <= (2k+1)π, ω <= 4k + 3/4
因此,综合 ω > 0, ω <= 1/2, 因此选 D
追问那个...sprt(2)是什么意思呢?
追答根号2
追问谢谢!