已知函数f(x)=4sin2(π/4 +x)-2√3cos2x-1,且给定条件p:xπ/2,x∈R.⑴在非p的条件下,求f(x)的最值;⑵若条件q:-2<f(x)-m<2且非p是q的充分条件,求实数m的取值范围。
你们看啊,解析
f(x)=4sin2(π/4 +x)-2√3cos2x-1
=-2[1-2sin2(π/4 +x)]-2√3cos2x+1
=-2cos(π/2 +2x)-2√3cos2x+1
=2sin2x-2√3cos2x+1
=4sin(2x -π/3)+1
1)非p的条件下,x∈[π/4 ,π/2]
则2x∈[π/2 ,π]
2x-π/3∈[π/6 ,2π/3]
f(x)最小值=3
f(x)最大值=5
2)条件q
f(x)-m
=4sin(2x -π/3)+1-m∈(-2,2)
则,4sin(2x -π/3)+1∈(m-2,m+2)
非p的条件下2x-π/3∈[π/6 ,2π/3]
4sin(2x -π/3)+1∈[3,5]
非p是q的充分条件
==>m>5或m5 ==〉m∈(5,7]
mm∈[-3,3)
===>实数m的取值范围m∈[-3,3)∪(5,7]
解完后,男生来句,学霸就是学霸,这么难都能解