MATLAB: Help! plotting i(t) vs t.

help! plotting i(t) vs t.homework

Hello, i got stocked bulding my code for this problem.
      a) plot i(t) vs. t, over -pi<t<3pi.       i(t)= {3+5*sin(2*t-pi)+t*exp(-t)}[u(t)-u(t-2*pi)]      b) determine the values for i(t) for t = 0, pi/2, pi and -pi/2      c) evaluate RMS value of i(t)
This is what I have so far:
      % Script file : sym _ analysis _ RLC      % Analysis of an RLC series circuit      % where the current is iamps i(t)= {3+5*sin(2*t-pi)+t*exp(-t)}[u(t)-u(t-2*pi)]      % R=2K Ohms, L=3mH, and C=1 microF      function i(t) = ?????      u = double(t>=0);      echo off;      iamps= {3+5*sin(2*t-pi)+t*exp(-t)}*(u(t)-u(t-2*pi));      figure(1)      subplot(2,2,1)      ezplot(iamps)      title('i(t) vs.t');      ylabel('Amplitude (amps)');      grid on
ALL advice will be really appreciated.
Thanks.

function iamps = i(t)
iamps = (3+5*sin(2*t-pi)+t*exp(-t))*(u(t)-u(t-2*pi));  %{} became ()
   iamps = (3+5*sin(2*t-pi)+t.*exp(-t)).*(u(t)-u(t-2*pi));  %vectorize as well