f(x)=1-2a-2acosx-2sin^2x
f(x)=1-2a-2acosx-2sin^2x
=1-2a-2acosx-2(1-cos^2x)
=1-2a-2acosx-2+2cos^2x
=2cos^2x-2acosx-2a-1
=2(cos^2x-acosx)-2a-1
=2(cos^2x-acosx+a^2/4)-a^2/2-2a-1
=2(cosx-a/2)^2-a^2/2-2a-1
当cosx-a/2=0时,f(x)的值最小(-2
f(x)=1-2a-2acosx-2sin^2x
f(x)=1-2a-2acosx-2sin^2x
=1-2a-2acosx-2(1-cos^2x)
=1-2a-2acosx-2+2cos^2x
=2cos^2x-2acosx-2a-1
=2(cos^2x-acosx)-2a-1
=2(cos^2x-acosx+a^2/4)-a^2/2-2a-1
=2(cosx-a/2)^2-a^2/2-2a-1
当cosx-a/2=0时,f(x)的值最小(-2