Write general purpose m-files to 1. multiply two signals 2. add and subtract two signals 3. shift signals by any sample generate two sinusoidal signals of the form cos (on). with 01 = b/10 and 02 = b/5, where b is your birth month, test the three functions and plot the results including x1 (n) = cos (n01) and x2 (n) = cos (n 02) let the signals you consider span the indices from -b to +b, where b is your birth month, too.