A question about P(w|t) in the tutorial

[ThomasDing2016]

In section 4 of the file "An Evening with... EM!", it shows the following:

and finally we have:

I know .

My question is: how do we get P(w|t) ?

[dirkhovy]

P(w|t) is one of the parameters we compute with EM: the emission probabilities. The other one, P(T) (or, more preciselt, P(t2|t1)) are the transition probabilities. The fact that we need both, but know neither, is what makes this problem so tricky, and it's also why EM is so helpful.