f(x)=3sin(2x+π/3),则比较f(1),f(2),f(3)三者大小、怎么比啊?
问题描述:
f(x)=3sin(2x+π/3),则比较f(1),f(2),f(3)三者大小、怎么比啊?
答
f(x)=-1时, 2x+π/3=-π/2+2kπ,x=kπ-5π/12
f(x)=1时,2x+π/3=π/2+2kπ,x=kπ+π/12
也就是f(x)在(kπ-5π/12,kπ+π/12)之间单调递增
在(kπ+π/12,kπ+7π/12)之间单调递减
7π/12时取最小值,而且在(-5π/12,19π/12)之间,距离7π/12越近,值越小.
7π/12≈1.83
那么f(3)>f(1)>f(2)