求函数y=3sin(π/3-2x)的单调增区间

问题描述:

求函数y=3sin(π/3-2x)的单调增区间

2kπ-π/2≤π/3-2x≤2kπ+π/2
解不等式得-kπ-π/12≤x≤-kπ+5π/12
所以函数y=3sin(π/3-2x)的单调增区间为【-kπ-π/12,-kπ+5π/12】(k属于z)

-π/2+2kπ≤π/3-2x≤π/2+2kπ -π/4+kπ≤π/6-x≤π/4+kπ -π/12-kπ≤x≤5π/12-kπ
[-π/12+kπ,5π/12+kπ]

y=3sin(π/3-2x)
=-3sin(2x-π/3)
在2x-π/3∈(2kπ+π/2,2kπ+3π/2)时单调增
故单调增区间是:
x∈(kπ+5π/12,kπ+11π/12) k∈Z
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