f(x)= -(cosx)^2-4t*sin(x/2)*cos(x/2)+2*t^2-6t+2
=-(1-sin²x)-2tsinx+2tsinx+2t²-6t+2
=sin²x-2tsinx+t²+t²-6t+1
=(sinx-t)²+t²-6t+1
1、(1)当t>1时,sinx=1时最小,g(t)=2t²-8t+2
(2)当-1≤t≤1时,g(t)=t²-6t+1
(3)当t
f(x)= -(cosx)^2-4t*sin(x/2)*cos(x/2)+2*t^2-6t+2
=-(1-sin²x)-2tsinx+2tsinx+2t²-6t+2
=sin²x-2tsinx+t²+t²-6t+1
=(sinx-t)²+t²-6t+1
1、(1)当t>1时,sinx=1时最小,g(t)=2t²-8t+2
(2)当-1≤t≤1时,g(t)=t²-6t+1
(3)当t