clear all;
close all;
clc;

d=10;

t = 1:0.1:20;
x = 80*t - 5*t.*sin(t) ;
y = t.^2 + cos(t);

plot(x,y)
hold on;

line1=[];
line2=[];
for i=2:length(t)
    
    k = (y(i)-y(i-1))/(x(i)-x(i-1));
    
    k1 = -1/k;
    b1 = y(i)-k1*x(i);
    
    tmp = sqrt(-b1^2 + d^2 + d^2*k1^2 - 2*b1*k1*x(i) - k1^2*x(i)^2 + 2*b1*y(i) + 2*k1*x(i)*y(i) - y(i)^2);
    
    x1 = (-b1*k1 + x(i) + k1*y(i) - tmp)/(1 + k1^2);
    y1 = b1 - (b1*k1^2)/(1 + k1^2) + (k1*x(i))/(1 + k1^2) + (k1^2*y(i))/(1 + k1^2) - (k1*tmp)/(1 + k1^2);
    
    x2 = (-b1*k1 + x(i) + k1*y(i) + tmp)/(1 + k1^2);
    y2 = b1 - (b1*k1^2)/(1 + k1^2) + (k1*x(i))/(1 + k1^2) + (k1^2*y(i))/(1 + k1^2) + (k1*tmp)/(1 + k1^2);
    
    line1=[line1;x1 y1];
    line2=[line2;x2 y2];
end
plot(line1(:,1),line1(:,2),'r');
plot(line2(:,1),line2(:,2),'r');

axis equal