P(t)=25sin(35t) euler method

%i need help with my getder file which take the derivative of the funtion.
%there are 3 file main where define all variables getder which i obtain the derivative
%and box_solve to solve and create a plot using eulers or RK method.
%Many thanks in advance

%main file 
v0 = 0;
s0 = 0;
m = .5;
k = 75;
%getder file to obtain a the derivative
function xdot = getder(t,x)
x = [s;v];
a = (1/m)*(25*sin(45*t)-k*so);
xdot = [s;a];

%box_solve file to solve equation through euler method or Rk.
function [t,x] = box solve(x0,tlim,dt,solve_type)

if st == 1 %solve type allow operator to 
    t = (to:dt:tf).'
    L = length(t);
    x = xeros([l,2])
    x(1,:) = xo.'
    for n =1:L
        x(n+1,:) = x(n,:)+dt*geter(t(n),x(n,:));

[MANIK]

Hi @Fernando Piedra,

Can you be please more clear regarding your doubt in the code?

Answer 1

[Jon]

Just glancing at your code I can see a number of errors:

The variable s is not defined anywhere before you call this line of code in getder

x = [s;v];

So, MATLAB will not know how to make that assignment since it doesn't know what s is.

In the next line of code

a = (1/m)*(25*sin(45*t)-k*so);

It looks like you have a variable called so (also not defined) you probably meant s0 (that's the number zero as the second character rather than the letter o)

In this line you do not use a valid name for the function. You can not have spaces in a function name.

function [t,x] = box solve(x0,tlim,dt,solve_type)

You probably have even more errors but that should at least get you started