−12<σ<12-\dfrac{1}{2}<\sigma <\dfrac{1}{2}−21<σ<21
−12<σ<1-\dfrac{1}{2}<\sigma <1−21<σ<1
1<σ<21<\sigma <21<σ<2
−1<σ<12-1<\sigma <\dfrac{1}{2}−1<σ<21
