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问题: 高一数学题

f(x)=sin^4x+cos^4x+sin^2x/2-sin2x
要详细步骤
多谢

解答:

是求最值?或是值域?

解:
f(x)=sin^4x+cos^4x+sin^2x/2-sin2x
=1+sin^2x/2-sin2x
=1+(1/2)(sin^2x-2sin2x)
=1+(1/2)(sin^2x-2sin2x1-1)
=1+(1/2)(sin^2x-1)^2 -(1/2)
=(1/2)(sin^2x-1)^2 +(1/2)
当sin2x=1时,fmin=1/2
当sin2x=-1时,fmax=5/2
y∈[1/2,5/2]