# Working out location of a hydraulic jump

This is the question I am working on:

And here is part of the working i don't understand:

I don't understand the process of plotting the profile - the little crosses marked on the diagram, how do you determine those? It says "plot sequent depths from jump equation taking d1 from upstream profile". So I used d1 = 1.2m and solved for d2 using the equation $$d_2=\frac{d_1}{2}\times(\sqrt{1+\frac{8q^2}{g{d_1}^3}}-1)$$ and obtained $$d_2=4.24m$$ (I used q = 11.64 from previous calculations) What exactly is that telling me though, am i even on the right track?