庄子送葬，过惠子之墓，顾谓从者曰:"郢人垩漫其鼻端，若蝇翅，使匠石斫之。匠石运斤成风，听而斫之，尽垩而鼻不伤。郢人立不失容，宋元君闻之，召匠石曰:"尝试为寡人为之。"匠石曰:"臣则尝能斫之。虽然，臣之质死久矣。" 自夫子之死也，吾无以为质，吾无与言之矣。”
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clear all; close all; clc
xlist = -2: 0.01 : 2.5 ;
ylist = xlist.^2 - 2 ;
xlist2 = xlist;
ylist2 = zeros(1, length(xlist2));
ylist3 = -3: 0.01 : 4 ;
xlist3 = zeros(1, length(ylist3));
x0 = 2;
fx0 = x0^2 - 2 ;
xlist4 = x0 + (-1:0.01:1);
ylist4 = fx0 + 2* x0 * (-1: 0.01 : 1);
x1 = 1/2 * (x0 + 2/x0);
ylist5 = -1 : 0.01 : 1;
xlist5 = x1 * ones(1, length(ylist5));
fx1 = x1^2 - 2 ;
xlist6 = x1 + (-1:0.01:1);
ylist6 = fx1 + 2* x1 * (-1: 0.01 : 1);
plot(xlist, ylist, xlist2, ylist2, xlist3, ylist3)
hold on
plot(xlist4, ylist4,":","linewidth",2)
plot(xlist5, ylist5)
plot(xlist6, ylist6,":","linewidth",2)
