求函数y=sin(π/3-x/2),x∈[-2π,2π]的单调递增区间.求详解,

问题描述:

求函数y=sin(π/3-x/2),x∈[-2π,2π]的单调递增区间.求详解,

求函数y=sin(π/3-x/2),x∈[-2π,2π]的单调递增区间
y=sin(π/3-x/2)=-sin(x/2-π/3)
用五点作图法,列表计算,画图,不难确定在x∈[-2π,2π]范围内的单调递减区间
为[-π/3,5π/3]
因为y(-π/3)=-sin(-π/6-π/3)=-sin(-π/2)=1;
y(5π/3)=-sin(5π/6-π/3)=-sin(π/2)=-1.

y=sin(π/3-x/2)=-sin(x/2-π/3)
增区间,即y=sin(x/2-π/3)的减区间
∴ 2kπ+π/2≤x/2-π/3≤2kπ+3π/2
即 4kπ+5π/3≤x≤4kπ+11π/3
结合x∈[-2π,2π]
增区间是[5π/3,2π] 和[-2π,-π/3]