∵f(sinα)≥0,f(2+cosβ)≤0
∴f(1)≥0,f(2-1)≤0
∴f(1)=0
1+b+c=0
b+c=-1
f(2+1)≤0
9+3b+c≤0
9+3(-1-c)+c≤0
c≥3
f(sinα)≤8
1-b+c≤8
1-(-c-1)+c≤8
c≤3
∴c=3
∴b=-4
∵f(sinα)≥0,f(2+cosβ)≤0
∴f(1)≥0,f(2-1)≤0
∴f(1)=0
1+b+c=0
b+c=-1
f(2+1)≤0
9+3b+c≤0
9+3(-1-c)+c≤0
c≥3
f(sinα)≤8
1-b+c≤8
1-(-c-1)+c≤8
c≤3
∴c=3
∴b=-4