f1=@(x) sqrt(x.^2-0.9);
f2=@(x) x./tan(x)-f1(x).*tan(f1(x));
x0=[];y0=[];
for ii=1:8
x0(ii)=fzero(f2,pi/4+pi/2*(ii-1)); %å©ç¨fzeroæ±äº¤ç¹ï¼æ¯pi/2æä¸ä¸ªäº¤ç¹
y0(ii)=f1(x0(ii));
end
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%æ ¹æ®å½æ°ç对称æ§ï¼å¯ä»¥ç¥é (x0,-y0)(-x0,-y0)(-x0,y0)ä¹æ¯äº¤ç¹
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xl=linspace(0,4*pi,1000);
[x,y]=meshgrid(xl);
z1=x./tan(x)-y.*tan(y);
z1(abs(z1)>100)=nan;
yl=f1(xl);
contour(x,y,z1,[0 0]); %ç»åºx./tan(x)-y.*tan(y)=0çå½æ°å¾å
hold on;
plot(xl,yl,'r'); %ç»åº x^2-y^2=0.9çå½æ°å¾å
plot(x0,y0,'k.');%ç»åºäº¤ç¹
hold off;
axis image