t = 0:st:2*pi;
r = 664.6;
x = r*cos(t);
y = r*sin(t);
x2 = linspace(0,2*pi*r,length(t)); % 等分圓周點與 t 相同
rr = 25*sin(x2)+r;
x2 = rr.*cos(t);
y2 = rr.*sin(t);
plot(x,y,'b:');
axis square
hold on
plot(x2,y2,'r-');
hold off