Question

求函数y=cos2x-sin^2x-3sinx+3的最大值与最小值.

Answer 1

令t=sinx,

则cos2x=1-2t^2,

y=1-2t^2-t^2-3t+3=-3t^2-3t+4=-3(t+1/2)^2+19/4

因为|t|