已知函数f(x)=2sin(-3x+π/4),高手快来已知函数f(x)=2sin(-3x+π/4)(1)求f(x)的单调递增区间(这一题仅供参考下题,可以不做)(2)当f(x)大于等于根号2时,求x的取值范围(答案是[π/2+2kπ/3,2π/3+2kπ/3](k∈Z)怎么做?谢谢
问题描述:
已知函数f(x)=2sin(-3x+π/4),高手快来
已知函数f(x)=2sin(-3x+π/4)
(1)求f(x)的单调递增区间(这一题仅供参考下题,可以不做)
(2)当f(x)大于等于根号2时,求x的取值范围(答案是[π/2+2kπ/3,2π/3+2kπ/3](k∈Z)怎么做?谢谢
答
(1)f(x)=2sin(-3x+π/4)=-2sin(3x-π/4)∵2kπ+π/2≤3x-π/4≤2kπ+2π/3,k∈Z∴2kπ/3+π/4≤x≤5π/12+2kπ/3,k∈Z∴f(x)的单调递增区间[2kπ/3+π/4,5π/12+2kπ/3],k∈Z(2)∵f(x)=-2sin(3x-π/4)≥√2∴sin(3x-...