Real Solution of an Equation and Plot it

Hello Friends,

I want to know the solution of the given below equation using Mathcad Prime 3.1.

In above equation, two variable i.e. Phi. & Zeta is given but need to find out Psi.

There is a figure given for reference which tells the relation in these variable as attache herein post.

Can anyone tell me how to calculate Psi using the given references and also if I need to plot it, then how can it be achived.

Thanks, Yogesh