看了你写的，还是多学习一下书（线性代数和Matlab）吧，线性代数告诉你什么叫矩阵，Matlab告诉你软件规则。 修改如下，已调试，请运行
l1=2000/3;
l2=1000;
r1=40;
r2=20;
r3=60;
for i=1:91  %(pi/2/(pi/180)+1)
    x(i)=(i-1)*pi/180;  %x一维矩阵
    y(i)= r1*(pi/2-x(i)+asin((r1-r2)/l1))+r3*(pi/2-acos((l2^2-l1*l2*cos(x(i)))/(l2*sqrt(l1^2+l2^2-2*l1*l2*cos(x(i)))))+...
        asin((r3-r2)/sqrt(l1^2+l2^2-2*l1*l2*cos(x(i)))))+r2*(x(i)+acos((l2^2-l1*l2*cos(x(i)))/(l2*sqrt(l1^2+l2^2-2*l1*l2*cos(x(i)))))-...
        asin((r1-r2)/l1)-asin((r3-r2)/sqrt(l1^2+l2^2-2*l1*l2*cos(x(i)))))+...
        sqrt(l1^2-r1^2-r2^2+2*r1*r2)+sqrt(l1^2+l2^2-2*l1*l2*cos(x(i))-r3^2-r2^2+2*r3*r2);
end
plot(x,y,'r-');
grid on;