@Kitonum Thanks, that is what I was trying. Thak you so much for the help.

@Kitonum I know that the equation will get the error if the value o f_z=0, because it will never happen.
the equation of Z was correctly, Z := 892/(27417000*f_z);
 

I will leave a little text where i get the equation and the parameters, maybe I am not explaining it correctly.

The values of s must be like this graph:

Thanks for your help.

@Kitonum Sorry Mister

I misunderstood the real value of s_0. It is the value of the first interaction to garantee that the convergeance point is right.

Thus the interactions must get start from this point to each value of f_z.

Can I add this term as well?

Thanks for all.

@Kitonum 

Thanks for the answer and the additional plot too.

But I need to add the initial condition as well

s:=s_0 and

s_0 := (1/4)*Pi-1/2*(b_u-y_f)

when f_z:=0

I'm sorry,

i edited the question and put the code to simplify, Thansk

I put the code wrong, in the maple I have used Pi.

Thanks