Question

已知f（x）=-sin方x-cosx+四分之九,x属于R,求f（x）的最大值和最小值.

Answer 1

令 t =cos x,

则 f(x) =g(t)

= -(1 -t^2) -t +9/4

=t^2 -t +5/4

=(t-1/2)^2 +1, -1 ≤t ≤1.

(1) 当 t =1/2 时,

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