f(x)=根号3sin2x+2sin(π/4+x)sin(π/4-x)
2个回答

f(x)=根号3sin2x+2sin[π/2-(π/4-x)]sin(π/4-x)

=根号3sin2x+2cos(π/4-x)sin(π/4-x)

=根号3sin2x+sin(π/2-2x)

=根号3sin2x+cos2x

=2(根号3/2sin2x+1/2cos2x)

=2(cosπ/6sin2x+sinπ/6cos2x)

=2sin(2x+π/6)

最小正周期 T=2π/2=π

2kπ-π/2≤2x+π/6≤2kπ+π/2

2kπ-2π/3≤2x≤2kπ+π/3

kπ-π/3≤x≤kπ+π/6 (k∈Z)

∴单调递增区间为 [kπ-π/3 ,kπ+π/6 ] (k∈Z)

当x∈(0,π/2]

∴2x+π/6 ∈ (π/6 , 7π/6]

f(x)max=f(π/6)=2

f(x)min=f(0)=1

∴当 x∈(0,π/2] 时

值域为(0 , 2]

好辛苦啊! 慌忙中不知道有没有错误,若有的话望见谅哈!