a=get(handles.text1,'String'); %get the string from the textbox,example %a='t^2';
b=vectorize(a); %put dots before operations ^ / *
c=inline(b); %create one inline function from the string
t=0:0.1:10; %create a time vector, starts in t=0, step 0.1 seconds, ends t=10 s
c(t); %evaluate your function at each time vector point
For the fourier problem, t should be defined like a symbolic variable before the function being called
syms t
