求函数y=2sin(π/4-2x)的单调递减区间

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求函数y=2sin(π/4-2x)的单调递减区间
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求函数y=2sin(π/4-2x)的单调递减区间
求函数y=2sin(π/4-2x)的单调递减区间

求函数y=2sin(π/4-2x)的单调递减区间
y=-2sin(2x-π/4)
y递减则sin(2x-π/4)递增
sinx增区间是(2kπ-π/2,2kπ+π/2)
则2kπ-π/2

函数y=2sin(π/4-2x)的单调递减区间
就是函数y=2sin(2x-π/4)的单调递增区间
函数y=2sin(2x-π/4)的单调递增区间
2kπ-π/2<=2x-π/4<=2kπ+π/2
[kπ-π/8,kπ+3π/8]
函数y=2sin(π/4-2x)的单调递减区间 是
[kπ-π/8,kπ+3π/8]

y‘ = 2sin(π/4-2x)' <= 0
2cos(π/4-2x)*2<=0
cos(π/4-2x)<=0
2nπ+ π/2 <=π/4-2x <= 2nπ +3π/2
-π/4 - 2nπ >= 2x >= -5π/4 - 2nπ
nπ -π/8 > x >nπ - 5π/4
及单调递减区间为: [nπ-5π/8, nπ-π/8]