function ret=inv_abs(num) ret=[abs(num) -abs(num)];. ... <看更多>

plot(abs(fftshift(ut)));. % the 2 * pi / L is to get to rescale because Matlab thinks everything is 2*pi. % the next part is frequency numbers. ... <看更多>

Hint: This is equal to 2exp(3)cos(4). If you want to do it with MATLAB close all; clear all; clc; ... ... <看更多>