In the video about gradient checking is said that we “concatenate all the parameters b[l] W[l] y one vector theta” and then, theta(i) is used.

I’m not sure if theta(i) stands for a whole parameter (vector o matrix) W (or b), or instead it stands form uno of the components of this parameters.

In other words, if you have

W=[1, 2, 3

4, 5, 6]

and

b = [7, 8]

theta(1) would be [[1, 2, 3], [4, 5, 6]] or 1?

Thanks in advance!