求函数y=-cos^2x-sinx+1 x∈[π/4,3π/4]如题

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求函数y=-cos^2x-sinx+1x∈[π/4,3π/4]如题求函数y=-cos^2x-sinx+1x∈[π/4,3π/4]如题求函数y=-cos^2x-sinx+1x∈[π/4,3π/4]如题求

求函数y=-cos^2x-sinx+1 x∈[π/4,3π/4]如题
求函数y=-cos^2x-sinx+1 x∈[π/4,3π/4]
如题

求函数y=-cos^2x-sinx+1 x∈[π/4,3π/4]如题
求函数y=-cos^2x-sinx+1 x∈[π/4,3π/4]的值域.
y=sin^2x-sinx
=(sinx-1/2)^2-1/4
x∈[π/4,3π/4],
√2/2≤sinx≤1,
当sinx=√2/2,ymin=(1-√2)/2.
当sinx=1时,ymax=0.
∴值域[=(1-√2)/2,0].

[0.283,1]

是求值域吗?
[(1-2^(1/2))/2,0]