y=-2sin(x+π/4)-1
x∈R,y∈[-3,1]
x∈[π/2,π],y∈[-√2-1,√2-1]
y=sin²x-sinx+1
=(sinx-0.5)²+0.75
x∈R,y∈[0.75,3]
x∈[π/2,π],y∈[0.75,1]