函数f(x)=2sin(x-4/π)-sin2x的值域为

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函数f(x)=2sin(x-4/π)-sin2x的值域为

函数f(x)=2sin(x-4/π)-sin2x的值域为
函数f(x)=2sin(x-4/π)-sin2x的值域为

函数f(x)=2sin(x-4/π)-sin2x的值域为
f(x)=2sin(x-4/π) - sin2x
=2sin(x-π/4)- sin2x
=2sin(x-π/4)- cos(2x-π/2)
=2sin(x-π/4)- cos[2(x-π/4)]
=2sin(x-π/4)- 1+2sin^2(x-π/4)
=2sin^2(x-π/4)+ 2sin(x-π/4)- 1
=2[sin(x-π/4)+1/2]^2-3/2
-1 ≤ sin(x-π/4)≤ 1
-1/2 ≤ sin(x-π/4)+1/2 ≤ 3/2
0 ≤ [sin(x-π/4)+1/2]^2 ≤ 9/4
0 ≤ 2[sin(x-π/4)+1/2]^2 ≤ 9/2
-3/2 ≤ 2[sin(x-π/4)+1/2]^2-3/2 ≤ 3
值域【-3/2,3】

因为1-sin2x=(sinx-cosx)^2=2sin^2(x-
π/4),所以f(x)+1=2sin(x-π/4)-sin2x+1=2(sin(X-π/4)+0.5)^2-0.5
又sin(x-π/4)范围为[-1,1],所以f(x)+1值域为[-0.5,4]所以f(x)值域为[-1.5,3]