The Brewsters angle $i_b$ for an interface should be:

Brewster's law states $\tan i_b=\mu$.Since $\mu >1$ for most media (like glass, water) into air,$\tan i_b>1\Rightarrow i_b>45^{\circ }$.Also, since $\mu$ is finite, $i_b<90^{\circ }$.So, $45^{\circ }<i_b<90^{\circ }$.