y=cos2x +2sinx -3的值域= 1-2(sinx)^2+2sinx -3= -2(sinx-1/2)^2 - 3/2 _数学解答

y=cos2x +2sinx -3的值域
= 1-2(sinx)^2+2sinx -3
= -2(sinx-1/2)^2 - 3/2 值域为[-6,-3/2]是怎么算出来的,

人气：423 ℃　时间：2020-04-02 11:03:14

解答

y= -2(sinx-1/2)^2 - 3/2
因为-1<=sinx<=1
所以sinx=1/2,最大-3/2
sinx=-1,最小是-6