%% 直线为轴中心对称的圆

clc;

clear;

hold on

syms x y;

% 画对称轴

x1=-20:0.1:20;

k=1;

b1=10;

f1(x)=k.*x+b1;

plot(x1,f1(x1));

theta=0:2*pi/3600:2*pi;

R=4;

Circle1=10+R*cos(theta);

Circle2=10+R*sin(theta);

plot(Circle1,Circle2,'m','Linewidth',3);

x1=Circle1;

y1=Circle2;

% 对称点坐标(2*x0-x1,2f(x0)-y1)

b0=y1+(1/k).*x1;

x0=(b0-b1).*(k/(k^2+1));

x2=2*x0-x1;

y2=2*f1(x0)-y1;

plot(x2,y2,'r-');

axis equal

%% 直线为轴中心对称的三角形

close all; clear all; clc

hold on

x1=-20:0.1:20;

syms x

k=1/2;

b1=4;

f1(x)=k.*(x+2)+b1;

plot(x1,f1(x1),'b');

x1=1;x2=2;x3=1;

y1=1;y2=2;y3=3;

triangle_x1=[x1,x2,x3,x1];

triangle_y1=[y1,y2,y3,y1];

fill(triangle_x1,triangle_y1,'r');

% 对称点坐标(2*x0-x1,2f(x0)-y1)

b0=triangle_y1+(1/k).* triangle_x1;

x0=(b0-b1).*(k/(k^2+1));

triangle_x2=2*x0-triangle_x1;

triangle_y2=2*f1(x0)-triangle_y1;

% triangle_y2=[1,2,1,1];

fill(triangle_x2,triangle_y2,'b');

axis([-5 5 -5 30])

axis equal;

%% 点为中心对称的三角形

close all; clear all; clc

hold on

x0=1.5;

y0=2;

plot(x0,y0,'*')

x1=1;x2=2;x3=1;

y1=1;y2=2;y3=3;

triangle_x1=[x1,x2,x3,x1];

triangle_y1=[y1,y2,y3,y1];

fill(triangle_x1,triangle_y1,'r');

triangle_x2=2*x0-triangle_x1;

triangle_y2=2*y0-triangle_y1;

fill(triangle_x2,triangle_y2,'b');

axis equal;