Change or update an existing variable at iteration intervals in an iteration loop

I need to update the variable t with this same initilization formula when the iteration gets to iteration 10, iteration 15, iteration 25 and iteration 40. I tried this way but no changes.

    clc;clear;close all;
    
    MaxIt=50;
    P=3;
    xmin = randi(10);
    ymin = 100;
    x = [150 300 350];
    y = [500 700 850];
        
    %% Initialize variable t
    t=zeros(1,P);
    for i=1:P
        t(i)=sqrt((y(i)-ymin)+(x(i)-xmin));
    end
    
    %% Main loop
    Fanswer = zeros(MaxIt,1);
    for it=1:MaxIt
        F = t * pi * randi(10);
        GetCost = F(1);
    Fanswer(it)=GetCost;
    
    disp(['MaxIt' num2str(it) ': Get Cost =' num2str(Fanswer(it))]);

    %<------ This is where my problem is--------->
    % I need to calculate and update variable t again here after 10th, 
    % 15th, 25th and 40th iterations. I did it this way but didn't work.
    if (it)==[10 15 25 40]    
        for i=1:P
        t(i)=sqrt((y(i)-ymin)+(x(i)-xmin));
        end
    end
    end

Answer 1

[Sargondjani]

it==[10 15 25 40]

gives a vector as output. You want a scalar either 0 or 1:

Use:

ismember(it,[10 15 25 40])