Integral of a function with time variables.

Hello,

I try to calculate the integral of the following function:

F(t) = r + Integral from 0 to 20 of (D(p)*s(t-p)dp)

I tried it the following way, but get some errors:

f = r+(eval(int(sym('D*s*(p-tau)'),0,20)));

Error: ??? Error using ==> mupadmex Error in MuPAD command: Illegal integrand [int]

Error in ==> sym.int at 56 r = mupadmex('symobj::intdef',f.s,x.s,a.s,b.s);

Does anyone have a suggestion how to implement the integral correctly?

Answer 1

[Andrew Newell]

You've got multiple problems here. You haven't defined which variable you are integrating over. More importantly, in your problem statement D and s are functions, but in the integral you are treating them like constants. Here is an example of how you could calculate your integral, assuming you know what D and s actually are:

syms p r tau
D = cos(p);
s = sin(p-tau);
f = f = r + int(D*s,p,0,20);

Note also that the eval was unnecessary.