%% USING MATLAB TO SOLVE A HIGHER ORDER ODE %% % Here is an example of using MATLAB to solve an inhomogeneous higher order % differential equation. The equation is: %% % % \$\$y^{iv} \mbox{--} 2 y'' + y' = t^3 + 2e^t.\$\$ % eqn = 'D4y - 2*D2y + Dy = t^3 +2*exp(t)' %% % The notation *D4y* means the 4th derivative of |y|, *Dky* means the % kth derivative (where k is a positive integer). %% % I can solve this equation with the command *dsolve*. I'll call the solution % _sol_. I'll supress printing it, because the answer will give too long a % line, then use the command *pretty* to print it, which will make it fit % reasonably. sol = dsolve(eqn); pretty(sol) %% % In this case, the answer appears much too complicated. The next thing to % try is *simplify*. pretty(simplify(sol)) %% % I can also try *simple*. pretty(simple(sol)) %% % This has the terms in a different order from the previous answer but % isn't simpler. %% % Notice that the equation is fourth order and the solution depends on 4 % constants, C7, C8, C9 and C10.