求函数的值域：(1)y=cosx+3 (2)y=4sin^2x-2

求函数的值域：(1)y=cosx+3 (2)y=4sin^2x-2
求函数的值域：(1)y=cosx+3 (2)y=4sin^2x-2

求函数的值域：(1)y=cosx+3 (2)y=4sin^2x-2
(1)
cosx∈[-1,1]
则
y=cosx+3∈[2,4]
(2)y=4sin^2x-2
sinx∈[-1,1]
sin^2x∈[0,1]
则
y=4sin^2x-2∈[-2,2]

1、[2,4]
2、y=4sin^2x-2
=2( 2sin^2x-1)
=-2cos2x
[-2,2]