\[\theta_{n,m}^{(-\frac{1}{2},-\frac{1}{2})}=\frac{(m-\tfrac{1}{2})\pi}{n}\leq%
\theta_{n,m}^{(\alpha,\alpha)}\leq\frac{m\pi}{n+1}=\theta_{n,m}^{(\frac{1}{2},%
\frac{1}{2})},\]