matlab与微分几何的结合，用matlab程序实现曲面的第一基本量，第二基本量。

Question

r=[x,y,(x.^2)/(a.^2)+(y.^2)/(b.^2)];
rx=diff(r,x);
ry=diff(r,y);
E=simplify(dot(rx,rx));
F=simplify(dot(rx,ry));
G=simplify(dot(ry,ry));
rxx=simplify(diff(rx,x));
rxy=simplify(diff(rx,y));
ryy=simplify(diff(ry,y));
rcha=cross(rx,ry);
rchamo=norm(rcha);
n=simplify(rcha/rchamo);
L=simplify(dot(rxx,n));
M=simplify(dot(rxy,n));
 N=simplify(dot(ryy,n));

程序运行没有结果

Answer 1

clc
clear
syms x y a b
r=[x,y,(x.^2)/(a.^2)+(y.^2)/(b.^2)];
rx=diff(r,x);
ry=diff(r,y);
E=simplify(dot(rx,rx));
F=simplify(dot(rx,ry));
G=simplify(dot(ry,ry));
rxx=simplify(diff(rx,x));
rxy=simplify(diff(rx,y));
ryy=simplify(diff(ry,y));
rcha=cross(rx,ry);
rchamo=norm(rcha);
n=simplify(rcha/rchamo)
L=simplify(dot(rxx,n))
M=simplify(dot(rxy,n))
N=simplify(dot(ryy,n))

你这个全是符号变量，输出可以直接把需要输出的语句后面的分号;去掉，如果需要换成数字使用subs(f,x,a),即求解f=f（x），f（a）