Permanent establishment, b
Sin? x-b-3 & gt； =-4 with b
Permanent establishment, b
Single increasing function: cosx-b? ≥ sin? x-b-3
So cosx-sin? x+3 ≥ b？ -B.
Get 2+(cosx+ 1/2)? & gt= (b - 1/2)？
The minimum value on the left is 2, so1/2-√ 2 < = b <; = 1