plotting eta v/s iteration

I want to plot eta v/s iteration I dont know how to proceed

Answer 1

[KSSV]

N = 15 ; 
beta_a = 10;
alpha_n = 10 ;
eta = zeros(1,N) ; 
eta(1)=15;
for i=1:N-1
    
    theta_i = asind(sind(beta_a)*sind(eta(i)));
    theta_n = atand(tand(beta_a)*cosd(eta(i)))- alpha_n;
    
    phi_i = asind(sqrt(2)*sind(theta_i));
    phi_n = acosd(tand(theta_i)/tand(phi_i))-theta_n ;
    
    eta(i+1) = atand((tand(i)*cosd(phi_n-alpha_n)-cosd(alpha_n)*tand(phi_i))/sind(phi_n));
end
plot(1:N,eta)