求y=cos2x+2sinx-3的值域,
1个回答

y=1-2sinx^2+2sinx-3

=-2[sinx^2-sinx+(1/2)^2]-2+1/2

=-2(sinx-1/2)^2-3/2

因为:sinx∈[-1,1]

所以:y=cos2x+2sinx-3的值域求得为[-6,-3/2]