@Carl Love It was great.Thank you for your consideration.

@Carl Love 

Thanks, That's very helpful.

@samira moradi  For different values of B for example B=1, 2,3, ..30

@Carl Love  I find the toots in the following  method but I don't know  what range should I consider for L? 

restart;
B := 30;
y := 0.9;
k := 3/1000;
F := (sin(L)-tan(L*y)*cos(L))*((1-1/B)*L^2-k)+(L^3/B+L)*(cos(L)-tan(L*y)*sin(L));
lambda[1] := fsolve(F, L = 0 .. 1);

for i from 2 to 20 do

lambda[i] := fsolve(F, L = lambda[i-1] .. lambda[i-1]+Pi/(1.5)) end do;

@Carl Love Thanks, But I need all roots of this equation for example : 

for B=20

lambda[1] :=0 , lambda[2] :=.8624208614 , lambda[3] := 2.271578181

for B=10

lambda[1] := 0 , lambda[2] := 2.313847053, lambda[3] := 4.458711040

@acer Ok thanks for your attention.

@vv thanks for good answer. I need to calculate R-squre,too. How can I do that?

@vv Thanks for your attention.

@Carl Love

There is a problem with maple softwara, I cannot export data.

After I extracted the point data from the first plot How can I export the data in excel or other format ?

Thank you very much.

 I will show accuranty this equation with data. How can i fit experimental data with this plot?

thanks 

thanks for good answer.it helped me.