I'm not really sure how to approach this equation. Do the square brackets indicate a matrix? H(x) is just a vector of probabilities. What operation would I do first? i.e. would I end up with 1 figure, or a vector the same length as H(x)?

$\displaystyle t = \sqrt{ \ln \lbrack \frac {1}{(H(x))^2} \rbrack } $

Thanks for any help