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设函数f(x)=sin(2x+派/4)+cos(2x+派/4), 求函数对称轴和增减性. 要详细解答过程

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设函数f(x)=sin(2x+派/4)+cos(2x+派/4), 求函数对称轴和增减性. 要详细解答过程
设函数f(x)=sin(2x+派/4)+cos(2x+派/4), 求函数对称轴和增减性. 要详细解答过程
f(x)=sin(2x+派/4)+cos(2x+派/4)
=sin2xcos(π/4)+cos2xsin(π/4)+cos2xcos(π/4)-sin2xsin(π/4)
=√2cos(2x)
(1)2x=kπ
对称轴:x=kπ/2
(2)增区间
2kπ-π≤2x≤2kπ
kπ-π/2≤x≤kπ
增区间[kπ-π/2,kπ],k∈Z
减区间
2kπ≤2x≤2kπ+π
kπ≤x≤kπ+π/2
增区间[kπ,kπ+π/2],k∈Z
再问: =sin2xcos(π/4)+cos2xsin(π/4)+cos2xcos(π/4)-sin2xsin(π/4) =√2cos(2x) 这个……是怎么整理的……
再答: =sin2xcos(π/4)+cos2xsin(π/4)+cos2xcos(π/4)-sin2xsin(π/4) =(√2/2)sin2x+(√2/2)cos2x+(√2/2)cos2x-(√2/2)sin2x =√2cos2x